21661952400 has 405 divisors, whose sum is σ = 83000356257. Its totient is φ = 5227833600.

The previous prime is 21661952393. The next prime is 21661952407. The reversal of 21661952400 is 425916612.

The square root of 21661952400 is 147180.

It is a perfect power (a square), and thus also a powerful number.

21661952400 is a `hidden beast` number, since 2 + 1 + 66 + 195 + 2 + 400 = 666.

It is an interprime number because it is at equal distance from previous prime (21661952393) and next prime (21661952407).

It can be written as a sum of positive squares in only one way, i.e., 7798302864 + 13863649536 = 88308^2 + 117744^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21661952407) by changing a digit.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 97138689 + ... + 97138911.

Almost surely, 2^21661952400 is an apocalyptic number.

21661952400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

21661952400 is the 147180-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21661952400

21661952400 is an abundant number, since it is smaller than the sum of its proper divisors (61338403857).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661952400 is a wasteful number, since it uses less digits than its factorization.

21661952400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 492 (or 244 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

Multiplying 21661952400 by its sum of digits (36), we get a square (779830286400 = 883080²).

21661952400 divided by its sum of digits (36) gives a square (601720900 = 24530²).

The spelling of 21661952400 in words is "twenty-one billion, six hundred sixty-one million, nine hundred fifty-two thousand, four hundred".