21235913 has 4 divisors (see below), whose sum is σ = 21250320. Its totient is φ = 21221508.

The previous prime is 21235883. The next prime is 21235931. The reversal of 21235913 is 31953212.

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 21235913 - 2⁶ = 21235849 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21235933) 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, 4703 + ... + 8036.

It is an arithmetic number, because the mean of its divisors is an integer number (5312580).

Almost surely, 2^21235913 is an apocalyptic number.

It is an amenable number.

21235913 is a deficient number, since it is larger than the sum of its proper divisors (14407).

21235913 is a wasteful number, since it uses less digits than its factorization.

21235913 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14406.

The product of its digits is 1620, while the sum is 26.

The square root of 21235913 is about 4608.2440256566. The cubic root of 21235913 is about 276.9216936877.

The spelling of 21235913 in words is "twenty-one million, two hundred thirty-five thousand, nine hundred thirteen".