21678156 has 36 divisors (see below), whose sum is σ = 54940704. Its totient is φ = 7207200.

The previous prime is 21678143. The next prime is 21678161. The reversal of 21678156 is 65187612.

It is a tau number, because it is divible by the number of its divisors (36).

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 21678156.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 23341 + ... + 24251.

Almost surely, 2^21678156 is an apocalyptic number.

It is an amenable number.

21678156 is an abundant number, since it is smaller than the sum of its proper divisors (33262548).

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

21678156 is a wasteful number, since it uses less digits than its factorization.

21678156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1582 (or 1577 counting only the distinct ones).

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

The square root of 21678156 is about 4655.9806700630. The cubic root of 21678156 is about 278.8308220128.

The spelling of 21678156 in words is "twenty-one million, six hundred seventy-eight thousand, one hundred fifty-six".