21555600 has 240 divisors, whose sum is σ = 79709184. Its totient is φ = 4928000.

The previous prime is 21555593. The next prime is 21555607. The reversal of 21555600 is 655512.

It is an interprime number because it is at equal distance from previous prime (21555593) and next prime (21555607).

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is not an unprimeable number, because it can be changed into a prime (21555607) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 303565 + ... + 303635.

Almost surely, 2^21555600 is an apocalyptic number.

21555600 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 21555600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39854592).

21555600 is an abundant number, since it is smaller than the sum of its proper divisors (58153584).

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

21555600 is a wasteful number, since it uses less digits than its factorization.

21555600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 126 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 24.

The square root of 21555600 is about 4642.8008787800. The cubic root of 21555600 is about 278.3043782453.

It can be divided in two parts, 21555 and 600, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21555600 in words is "twenty-one million, five hundred fifty-five thousand, six hundred".