21239517 has 32 divisors (see below), whose sum is σ = 32175360. Its totient is φ = 12372480.

The previous prime is 21239507. The next prime is 21239551. The reversal of 21239517 is 71593212.

It is not a de Polignac number, because 21239517 - 2⁴ = 21239501 is a prime.

It is a super-2 number, since 2×21239517² = 902234164786578, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21239507) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 58984 + ... + 59342.

It is an arithmetic number, because the mean of its divisors is an integer number (1005480).

Almost surely, 2^21239517 is an apocalyptic number.

It is an amenable number.

21239517 is a deficient number, since it is larger than the sum of its proper divisors (10935843).

21239517 is a wasteful number, since it uses less digits than its factorization.

21239517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 453.

The product of its digits is 3780, while the sum is 30.

The square root of 21239517 is about 4608.6350473866. The cubic root of 21239517 is about 276.9373584930.

The spelling of 21239517 in words is "twenty-one million, two hundred thirty-nine thousand, five hundred seventeen".