21455431 has 2 divisors, whose sum is σ = 21455432. Its totient is φ = 21455430.

The previous prime is 21455429. The next prime is 21455443. The reversal of 21455431 is 13455412.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21455431 - 2¹ = 21455429 is a prime.

It is a super-2 number, since 2×21455431² = 920671038791522, which contains 22 as substring.

Together with 21455429, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21455396 and 21455405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21455461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10727715 + 10727716.

It is an arithmetic number, because the mean of its divisors is an integer number (10727716).

Almost surely, 2^21455431 is an apocalyptic number.

21455431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21455431 is an equidigital number, since it uses as much as digits as its factorization.

21455431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2400, while the sum is 25.

The square root of 21455431 is about 4632.0007556131. Note that the first 3 decimals coincide. The cubic root of 21455431 is about 277.8726147229.

The spelling of 21455431 in words is "twenty-one million, four hundred fifty-five thousand, four hundred thirty-one".