21097523 has 4 divisors (see below), whose sum is σ = 21219648. Its totient is φ = 20975400.

The previous prime is 21097513. The next prime is 21097547. The reversal of 21097523 is 32579012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21097523 - 2¹⁰ = 21096499 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21097513) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60803 + ... + 61148.

It is an arithmetic number, because the mean of its divisors is an integer number (5304912).

Almost surely, 2^21097523 is an apocalyptic number.

21097523 is a deficient number, since it is larger than the sum of its proper divisors (122125).

21097523 is a wasteful number, since it uses less digits than its factorization.

21097523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122124.

The product of its (nonzero) digits is 3780, while the sum is 29.

The square root of 21097523 is about 4593.2040015658. The cubic root of 21097523 is about 276.3188353132.

The spelling of 21097523 in words is "twenty-one million, ninety-seven thousand, five hundred twenty-three".