21272431 has 4 divisors (see below), whose sum is σ = 21282912. Its totient is φ = 21261952.

The previous prime is 21272429. The next prime is 21272437. The reversal of 21272431 is 13427212.

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 not a de Polignac number, because 21272431 - 2¹ = 21272429 is a prime.

It is a super-2 number, since 2×21272431² = 905032641299522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21272437) 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, 1111 + ... + 6616.

It is an arithmetic number, because the mean of its divisors is an integer number (5320728).

Almost surely, 2^21272431 is an apocalyptic number.

21272431 is a deficient number, since it is larger than the sum of its proper divisors (10481).

21272431 is an equidigital number, since it uses as much as digits as its factorization.

21272431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10480.

The product of its digits is 672, while the sum is 22.

The square root of 21272431 is about 4612.2045704847. The cubic root of 21272431 is about 277.0803374479.

Adding to 21272431 its reverse (13427212), we get a palindrome (34699643).

The spelling of 21272431 in words is "twenty-one million, two hundred seventy-two thousand, four hundred thirty-one".