21156451 has 8 divisors (see below), whose sum is σ = 21937104. Its totient is φ = 20388480.

The previous prime is 21156419. The next prime is 21156463. The reversal of 21156451 is 15465112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21156451 - 2⁵ = 21156419 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21156151) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 295 + ... + 6511.

It is an arithmetic number, because the mean of its divisors is an integer number (2742138).

Almost surely, 2^21156451 is an apocalyptic number.

21156451 is a deficient number, since it is larger than the sum of its proper divisors (780653).

21156451 is an equidigital number, since it uses as much as digits as its factorization.

21156451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6341.

The product of its digits is 1200, while the sum is 25.

The square root of 21156451 is about 4599.6142229539. The cubic root of 21156451 is about 276.5758604268.

The spelling of 21156451 in words is "twenty-one million, one hundred fifty-six thousand, four hundred fifty-one".