21688072 has 32 divisors (see below), whose sum is σ = 46696320. Its totient is φ = 9250560.

The previous prime is 21688067. The next prime is 21688109. The reversal of 21688072 is 27088612.

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

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, 12693 + ... + 14299.

It is an arithmetic number, because the mean of its divisors is an integer number (1459260).

Almost surely, 2^21688072 is an apocalyptic number.

It is an amenable number.

21688072 is an abundant number, since it is smaller than the sum of its proper divisors (25008248).

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

21688072 is a wasteful number, since it uses less digits than its factorization.

21688072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1861 (or 1857 counting only the distinct ones).

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

The square root of 21688072 is about 4657.0454152821. The cubic root of 21688072 is about 278.8733297023.

It can be divided in two parts, 216 and 88072, that added together give a palindrome (88288).

The spelling of 21688072 in words is "twenty-one million, six hundred eighty-eight thousand, seventy-two".