21687156 has 24 divisors (see below), whose sum is σ = 56226240. Its totient is φ = 7229016.

The previous prime is 21687119. The next prime is 21687191. The reversal of 21687156 is 65178612.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21687156.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 100296 + ... + 100511.

It is an arithmetic number, because the mean of its divisors is an integer number (2342760).

Almost surely, 2^21687156 is an apocalyptic number.

It is an amenable number.

21687156 is an abundant number, since it is smaller than the sum of its proper divisors (34539084).

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

21687156 is a wasteful number, since it uses less digits than its factorization.

21687156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200820 (or 200812 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21687156 is about 4656.9470686277. The cubic root of 21687156 is about 278.8694035570.

The spelling of 21687156 in words is "twenty-one million, six hundred eighty-seven thousand, one hundred fifty-six".