21456451 has 4 divisors (see below), whose sum is σ = 21472672. Its totient is φ = 21440232.

The previous prime is 21456439. The next prime is 21456469. The reversal of 21456451 is 15465412.

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 21456451 - 2⁵ = 21456419 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21456481) 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, 5931 + ... + 8836.

It is an arithmetic number, because the mean of its divisors is an integer number (5368168).

Almost surely, 2^21456451 is an apocalyptic number.

21456451 is a deficient number, since it is larger than the sum of its proper divisors (16221).

21456451 is a wasteful number, since it uses less digits than its factorization.

21456451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16220.

The product of its digits is 4800, while the sum is 28.

The square root of 21456451 is about 4632.1108579135. The cubic root of 21456451 is about 277.8770180459.

It can be divided in two parts, 214 and 56451, that added together give a palindrome (56665).

The spelling of 21456451 in words is "twenty-one million, four hundred fifty-six thousand, four hundred fifty-one".