21402431 has 6 divisors (see below), whose sum is σ = 22116096. Its totient is φ = 20711100.

The previous prime is 21402419. The next prime is 21402467. The reversal of 21402431 is 13420412.

It is not a de Polignac number, because 21402431 - 2¹⁰ = 21401407 is a prime.

It is a super-2 number, since 2×21402431² = 916128105419522, 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 (21402401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 10175 + ... + 12096.

It is an arithmetic number, because the mean of its divisors is an integer number (3686016).

Almost surely, 2^21402431 is an apocalyptic number.

21402431 is a deficient number, since it is larger than the sum of its proper divisors (713665).

21402431 is an equidigital number, since it uses as much as digits as its factorization.

21402431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22333 (or 22302 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21402431 is about 4626.2761482644. The cubic root of 21402431 is about 277.6436223239.

Adding to 21402431 its reverse (13420412), we get a palindrome (34822843).

The spelling of 21402431 in words is "twenty-one million, four hundred two thousand, four hundred thirty-one".