21132431 has 4 divisors (see below), whose sum is σ = 21243264. Its totient is φ = 21021600.

The previous prime is 21132383. The next prime is 21132481. The reversal of 21132431 is 13423112.

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 21132431 - 2²² = 16938127 is a prime.

It is a super-2 number, since 2×21132431² = 893159279939522, 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 (21132481) 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, 55130 + ... + 55511.

It is an arithmetic number, because the mean of its divisors is an integer number (5310816).

Almost surely, 2^21132431 is an apocalyptic number.

21132431 is a deficient number, since it is larger than the sum of its proper divisors (110833).

21132431 is a wasteful number, since it uses less digits than its factorization.

21132431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 110832.

The product of its digits is 144, while the sum is 17.

The square root of 21132431 is about 4597.0023928643. The cubic root of 21132431 is about 276.4711505532.

Adding to 21132431 its reverse (13423112), we get a palindrome (34555543).

The spelling of 21132431 in words is "twenty-one million, one hundred thirty-two thousand, four hundred thirty-one".