21231431 has 4 divisors (see below), whose sum is σ = 22864632. Its totient is φ = 19598232.

The previous prime is 21231421. The next prime is 21231433. The reversal of 21231431 is 13413212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21231431 is a prime.

It is a super-2 number, since 2×21231431² = 901547324615522, 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 (21231433) 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, 816581 + ... + 816606.

It is an arithmetic number, because the mean of its divisors is an integer number (5716158).

Almost surely, 2^21231431 is an apocalyptic number.

21231431 is a deficient number, since it is larger than the sum of its proper divisors (1633201).

21231431 is a wasteful number, since it uses less digits than its factorization.

21231431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1633200.

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

The square root of 21231431 is about 4607.7576976226. The cubic root of 21231431 is about 276.9022101778.

Adding to 21231431 its reverse (13413212), we get a palindrome (34644643).

The spelling of 21231431 in words is "twenty-one million, two hundred thirty-one thousand, four hundred thirty-one".