21597939 has 48 divisors (see below), whose sum is σ = 37031904. Its totient is φ = 11980800.

The previous prime is 21597931. The next prime is 21597949. The reversal of 21597939 is 93979512.

It is a happy number.

21597939 is a `hidden beast` number, since 21 + 597 + 9 + 39 = 666.

It is not a de Polignac number, because 21597939 - 2³ = 21597931 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21597894 and 21597903.

It is not an unprimeable number, because it can be changed into a prime (21597931) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 68847 + ... + 69159.

It is an arithmetic number, because the mean of its divisors is an integer number (771498).

Almost surely, 2^21597939 is an apocalyptic number.

21597939 is a deficient number, since it is larger than the sum of its proper divisors (15433965).

21597939 is a wasteful number, since it uses less digits than its factorization.

21597939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388 (or 385 counting only the distinct ones).

The product of its digits is 153090, while the sum is 45.

The square root of 21597939 is about 4647.3582818629. The cubic root of 21597939 is about 278.4864720363.

The spelling of 21597939 in words is "twenty-one million, five hundred ninety-seven thousand, nine hundred thirty-nine".