21097521 has 24 divisors (see below), whose sum is σ = 31414656. Its totient is φ = 13638240.

The previous prime is 21097513. The next prime is 21097547. The reversal of 21097521 is 12579012.

It is not a de Polignac number, because 21097521 - 2³ = 21097513 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21097121) 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 23 ways as a sum of consecutive naturals, for example, 45336 + ... + 45798.

It is an arithmetic number, because the mean of its divisors is an integer number (1308944).

Almost surely, 2^21097521 is an apocalyptic number.

It is an amenable number.

21097521 is a deficient number, since it is larger than the sum of its proper divisors (10317135).

21097521 is a wasteful number, since it uses less digits than its factorization.

21097521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 613 (or 610 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21097521 is about 4593.2037838528. The cubic root of 21097521 is about 276.3188265817.

The spelling of 21097521 in words is "twenty-one million, ninety-seven thousand, five hundred twenty-one".