21716451 has 8 divisors (see below), whose sum is σ = 32172560. Its totient is φ = 14477616.

The previous prime is 21716441. The next prime is 21716477. The reversal of 21716451 is 15461712.

It is a happy number.

21716451 is a `hidden beast` number, since 2 + 17 + 1 + 645 + 1 = 666.

It is not a de Polignac number, because 21716451 - 2⁷ = 21716323 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 804313 = 21716451 / (2 + 1 + 7 + 1 + 6 + 4 + 5 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21716441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 402130 + ... + 402183.

It is an arithmetic number, because the mean of its divisors is an integer number (4021570).

Almost surely, 2^21716451 is an apocalyptic number.

21716451 is a deficient number, since it is larger than the sum of its proper divisors (10456109).

21716451 is an equidigital number, since it uses as much as digits as its factorization.

21716451 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804322 (or 804316 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 21716451 is about 4660.0913081183. The cubic root of 21716451 is about 278.9949126139.

The spelling of 21716451 in words is "twenty-one million, seven hundred sixteen thousand, four hundred fifty-one".