21687492 has 24 divisors (see below), whose sum is σ = 51682176. Its totient is φ = 7075168.

The previous prime is 21687473. The next prime is 21687499. The reversal of 21687492 is 29478612.

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21687492.

It is not an unprimeable number, because it can be changed into a prime (21687499) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18663 + ... + 19790.

It is an arithmetic number, because the mean of its divisors is an integer number (2153424).

Almost surely, 2^21687492 is an apocalyptic number.

It is an amenable number.

21687492 is an abundant number, since it is smaller than the sum of its proper divisors (29994684).

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

21687492 is a wasteful number, since it uses less digits than its factorization.

21687492 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38507 (or 38505 counting only the distinct ones).

The product of its digits is 48384, while the sum is 39.

The square root of 21687492 is about 4656.9831436242. The cubic root of 21687492 is about 278.8708437279.

The spelling of 21687492 in words is "twenty-one million, six hundred eighty-seven thousand, four hundred ninety-two".