21197537 has 4 divisors (see below), whose sum is σ = 21278400. Its totient is φ = 21116676.

The previous prime is 21197489. The next prime is 21197551. The reversal of 21197537 is 73579112.

It is a happy number.

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 a de Polignac number, because none of the positive numbers 2^k-21197537 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21197497 and 21197506.

It is not an unprimeable number, because it can be changed into a prime (21197437) 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, 40037 + ... + 40562.

It is an arithmetic number, because the mean of its divisors is an integer number (5319600).

Almost surely, 2^21197537 is an apocalyptic number.

It is an amenable number.

21197537 is a deficient number, since it is larger than the sum of its proper divisors (80863).

21197537 is an equidigital number, since it uses as much as digits as its factorization.

21197537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80862.

The product of its digits is 13230, while the sum is 35.

The square root of 21197537 is about 4604.0783008111. The cubic root of 21197537 is about 276.7547821781.

The spelling of 21197537 in words is "twenty-one million, one hundred ninety-seven thousand, five hundred thirty-seven".