21685910400 has 1296 divisors, whose sum is σ = 99719867520. Its totient is φ = 4470681600.

The previous prime is 21685910383. The next prime is 21685910401. The reversal of 21685910400 is 401958612.

21685910400 is a `hidden beast` number, since 2 + 1 + 68 + 591 + 0 + 4 + 0 + 0 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21685910401) by changing a digit.

It is a polite number, since it can be written in 161 ways as a sum of consecutive naturals, for example, 170755137 + ... + 170755263.

Almost surely, 2^21685910400 is an apocalyptic number.

21685910400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21685910400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49859933760).

21685910400 is an abundant number, since it is smaller than the sum of its proper divisors (78033957120).

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

21685910400 is a wasteful number, since it uses less digits than its factorization.

21685910400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 155 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The spelling of 21685910400 in words is "twenty-one billion, six hundred eighty-five million, nine hundred ten thousand, four hundred".