21687028 has 24 divisors (see below), whose sum is σ = 41739264. Its totient is φ = 9777600.

The previous prime is 21686989. The next prime is 21687077. The reversal of 21687028 is 82078612.

It is a hoax number, since the sum of its digits (34) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21686984 and 21687002.

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, 3648 + ... + 7528.

It is an arithmetic number, because the mean of its divisors is an integer number (1739136).

Almost surely, 2^21687028 is an apocalyptic number.

It is an amenable number.

21687028 is a deficient number, since it is larger than the sum of its proper divisors (20052236).

21687028 is a wasteful number, since it uses less digits than its factorization.

21687028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4023 (or 4021 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 34.

The square root of 21687028 is about 4656.9333256984. The cubic root of 21687028 is about 278.8688549165.

The spelling of 21687028 in words is "twenty-one million, six hundred eighty-seven thousand, twenty-eight".