21587982 has 32 divisors (see below), whose sum is σ = 47295360. Its totient is φ = 6528480.

The previous prime is 21587963. The next prime is 21587987. The reversal of 21587982 is 28978512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21587987) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2257 + ... + 6947.

It is an arithmetic number, because the mean of its divisors is an integer number (1477980).

Almost surely, 2^21587982 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21587982, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23647680).

21587982 is an abundant number, since it is smaller than the sum of its proper divisors (25707378).

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

21587982 is a wasteful number, since it uses less digits than its factorization.

21587982 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4768.

The product of its digits is 80640, while the sum is 42.

The square root of 21587982 is about 4646.2869046153. The cubic root of 21587982 is about 278.4436698655.

The spelling of 21587982 in words is "twenty-one million, five hundred eighty-seven thousand, nine hundred eighty-two".