21320451 has 24 divisors (see below), whose sum is σ = 33218640. Its totient is φ = 13132800.

The previous prime is 21320447. The next prime is 21320479. The reversal of 21320451 is 15402312.

21320451 is a `hidden beast` number, since 213 + 2 + 0 + 451 = 666.

It is not a de Polignac number, because 21320451 - 2² = 21320447 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21320401) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5491 + ... + 8531.

It is an arithmetic number, because the mean of its divisors is an integer number (1384110).

Almost surely, 2^21320451 is an apocalyptic number.

21320451 is a deficient number, since it is larger than the sum of its proper divisors (11898189).

21320451 is a wasteful number, since it uses less digits than its factorization.

21320451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3107 (or 3104 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21320451 is about 4617.4073894340. The cubic root of 21320451 is about 277.2886728054.

Adding to 21320451 its reverse (15402312), we get a palindrome (36722763).

The spelling of 21320451 in words is "twenty-one million, three hundred twenty thousand, four hundred fifty-one".