21663216457 has 4 divisors (see below), whose sum is σ = 21740310036. Its totient is φ = 21586122880.

The previous prime is 21663216451. The next prime is 21663216479. The reversal of 21663216457 is 75461236612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6713508096 + 14949708361 = 81936^2 + 122269^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663216457 - 2¹¹ = 21663214409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21663216451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38546368 + ... + 38546929.

It is an arithmetic number, because the mean of its divisors is an integer number (5435077509).

Almost surely, 2^21663216457 is an apocalyptic number.

It is an amenable number.

21663216457 is a deficient number, since it is larger than the sum of its proper divisors (77093579).

21663216457 is an equidigital number, since it uses as much as digits as its factorization.

21663216457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77093578.

The product of its digits is 362880, while the sum is 43.

The spelling of 21663216457 in words is "twenty-one billion, six hundred sixty-three million, two hundred sixteen thousand, four hundred fifty-seven".