21097539 has 12 divisors (see below), whose sum is σ = 30817800. Its totient is φ = 13906464.

The previous prime is 21097513. The next prime is 21097547. The reversal of 21097539 is 93579012.

It is not a de Polignac number, because 21097539 - 2⁸ = 21097283 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21096539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12369 + ... + 13970.

It is an arithmetic number, because the mean of its divisors is an integer number (2568150).

Almost surely, 2^21097539 is an apocalyptic number.

21097539 is a deficient number, since it is larger than the sum of its proper divisors (9720261).

21097539 is a wasteful number, since it uses less digits than its factorization.

21097539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26434 (or 26431 counting only the distinct ones).

The product of its (nonzero) digits is 17010, while the sum is 36.

The square root of 21097539 is about 4593.2057432691. The cubic root of 21097539 is about 276.3189051650.

The spelling of 21097539 in words is "twenty-one million, ninety-seven thousand, five hundred thirty-nine".