21661600 has 36 divisors (see below), whose sum is σ = 52883334. Its totient is φ = 8664320.

The previous prime is 21661597. The next prime is 21661609. The reversal of 21661600 is 616612.

It can be written as a sum of positive squares in 3 ways, for example, as 19114384 + 2547216 = 4372^2 + 1596^2 .

It is not an unprimeable number, because it can be changed into a prime (21661609) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12739 + ... + 14338.

Almost surely, 2^21661600 is an apocalyptic number.

21661600 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21661600 is an abundant number, since it is smaller than the sum of its proper divisors (31221734).

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

21661600 is a wasteful number, since it uses less digits than its factorization.

21661600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27097 (or 27084 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21661600 is about 4654.2024021308. The cubic root of 21661600 is about 278.7598212202.

It can be divided in two parts, 216 and 61600, that added together give a palindrome (61816).

The spelling of 21661600 in words is "twenty-one million, six hundred sixty-one thousand, six hundred".