21097397 has 4 divisors (see below), whose sum is σ = 21455040. Its totient is φ = 20739756.

The previous prime is 21097393. The next prime is 21097421. The reversal of 21097397 is 79379012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21097397 - 2² = 21097393 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21097397.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21097393) 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, 178733 + ... + 178850.

It is an arithmetic number, because the mean of its divisors is an integer number (5363760).

Almost surely, 2^21097397 is an apocalyptic number.

It is an amenable number.

21097397 is a deficient number, since it is larger than the sum of its proper divisors (357643).

21097397 is an equidigital number, since it uses as much as digits as its factorization.

21097397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 357642.

The product of its (nonzero) digits is 23814, while the sum is 38.

The square root of 21097397 is about 4593.1902856294. The cubic root of 21097397 is about 276.3182852290.

The spelling of 21097397 in words is "twenty-one million, ninety-seven thousand, three hundred ninety-seven".