21956431 has 4 divisors (see below), whose sum is σ = 25093072. Its totient is φ = 18819792.

The previous prime is 21956423. The next prime is 21956461. The reversal of 21956431 is 13465912.

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 21956431 - 2³ = 21956423 is a prime.

It is a super-2 number, since 2×21956431² = 964169724515522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21956393 and 21956402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21956461) 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, 1568310 + ... + 1568323.

It is an arithmetic number, because the mean of its divisors is an integer number (6273268).

Almost surely, 2^21956431 is an apocalyptic number.

21956431 is a deficient number, since it is larger than the sum of its proper divisors (3136641).

21956431 is an equidigital number, since it uses as much as digits as its factorization.

21956431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3136640.

The product of its digits is 6480, while the sum is 31.

The square root of 21956431 is about 4685.7689870500. The cubic root of 21956431 is about 280.0188380183.

The spelling of 21956431 in words is "twenty-one million, nine hundred fifty-six thousand, four hundred thirty-one".