21266431 has 4 divisors (see below), whose sum is σ = 21275712. Its totient is φ = 21257152.

The previous prime is 21266411. The next prime is 21266449. The reversal of 21266431 is 13466212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21266431 is a prime.

It is a super-2 number, since 2×21266431² = 904522174955522, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21266396 and 21266405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21266411) 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, 1551 + ... + 6703.

It is an arithmetic number, because the mean of its divisors is an integer number (5318928).

Almost surely, 2^21266431 is an apocalyptic number.

21266431 is a deficient number, since it is larger than the sum of its proper divisors (9281).

21266431 is an equidigital number, since it uses as much as digits as its factorization.

21266431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9280.

The product of its digits is 1728, while the sum is 25.

The square root of 21266431 is about 4611.5540764475. The cubic root of 21266431 is about 277.0542843473.

The spelling of 21266431 in words is "twenty-one million, two hundred sixty-six thousand, four hundred thirty-one".