21655900 has 36 divisors (see below), whose sum is σ = 53708368. Its totient is φ = 7424640.

The previous prime is 21655897. The next prime is 21655901. The reversal of 21655900 is 955612.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21655901) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 14769 + ... + 16168.

Almost surely, 2^21655900 is an apocalyptic number.

21655900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21655900 is an abundant number, since it is smaller than the sum of its proper divisors (32052468).

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

21655900 is a wasteful number, since it uses less digits than its factorization.

21655900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30958 (or 30951 counting only the distinct ones).

The product of its (nonzero) digits is 2700, while the sum is 28.

The square root of 21655900 is about 4653.5900120230. The cubic root of 21655900 is about 278.7353682655.

The spelling of 21655900 in words is "twenty-one million, six hundred fifty-five thousand, nine hundred".