21423431 has 16 divisors (see below), whose sum is σ = 23760000. Its totient is φ = 19234656.

The previous prime is 21423421. The next prime is 21423487. The reversal of 21423431 is 13432412.

It is not a de Polignac number, because 21423431 - 2²² = 17229127 is a prime.

It is a super-2 number, since 2×21423431² = 917926791623522, 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 (21423421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32180 + ... + 32838.

It is an arithmetic number, because the mean of its divisors is an integer number (1485000).

Almost surely, 2^21423431 is an apocalyptic number.

21423431 is a deficient number, since it is larger than the sum of its proper divisors (2336569).

21423431 is a wasteful number, since it uses less digits than its factorization.

21423431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 766.

The product of its digits is 576, while the sum is 20.

The square root of 21423431 is about 4628.5452358165. The cubic root of 21423431 is about 277.7344003318.

Adding to 21423431 its reverse (13432412), we get a palindrome (34855843).

The spelling of 21423431 in words is "twenty-one million, four hundred twenty-three thousand, four hundred thirty-one".