21391587 has 96 divisors (see below), whose sum is σ = 41587200. Its totient is φ = 10777536.

The previous prime is 21391583. The next prime is 21391603. The reversal of 21391587 is 78519312.

It is not a de Polignac number, because 21391587 - 2² = 21391583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391583) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 578133 + ... + 578169.

It is an arithmetic number, because the mean of its divisors is an integer number (433200).

Almost surely, 2^21391587 is an apocalyptic number.

21391587 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21391587 is a deficient number, since it is larger than the sum of its proper divisors (20195613).

21391587 is a wasteful number, since it uses less digits than its factorization.

21391587 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102 (or 89 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21391587 is about 4625.1039988307. The cubic root of 21391587 is about 277.5967230399.

The spelling of 21391587 in words is "twenty-one million, three hundred ninety-one thousand, five hundred eighty-seven".