21264431 has 4 divisors (see below), whose sum is σ = 21463272. Its totient is φ = 21065592.

The previous prime is 21264427. The next prime is 21264449. The reversal of 21264431 is 13446212.

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 21264431 - 2² = 21264427 is a prime.

It is a super-2 number, since 2×21264431² = 904352051507522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21264397 and 21264406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21264421) 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, 99260 + ... + 99473.

It is an arithmetic number, because the mean of its divisors is an integer number (5365818).

Almost surely, 2^21264431 is an apocalyptic number.

21264431 is a deficient number, since it is larger than the sum of its proper divisors (198841).

21264431 is a wasteful number, since it uses less digits than its factorization.

21264431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198840.

The product of its digits is 1152, while the sum is 23.

The square root of 21264431 is about 4611.3372247104. The cubic root of 21264431 is about 277.0455988915.

The spelling of 21264431 in words is "twenty-one million, two hundred sixty-four thousand, four hundred thirty-one".