21450431 has 2 divisors, whose sum is σ = 21450432. Its totient is φ = 21450430.

The previous prime is 21450389. The next prime is 21450433. The reversal of 21450431 is 13405412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21450431 - 2⁶ = 21450367 is a prime.

It is a super-2 number, since 2×21450431² = 920241980171522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 21450433, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21450433) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725215 + 10725216.

It is an arithmetic number, because the mean of its divisors is an integer number (10725216).

Almost surely, 2^21450431 is an apocalyptic number.

21450431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21450431 is an equidigital number, since it uses as much as digits as its factorization.

21450431 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21450431 is about 4631.4610005915. The cubic root of 21450431 is about 277.8510277875.

Adding to 21450431 its reverse (13405412), we get a palindrome (34855843).

The spelling of 21450431 in words is "twenty-one million, four hundred fifty thousand, four hundred thirty-one".