21663204265553 has 4 divisors (see below), whose sum is σ = 21666496052148. Its totient is φ = 21659912478960.

The previous prime is 21663204265541. The next prime is 21663204265559. The reversal of 21663204265553 is 35556240236612.

It is a happy number.

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 9086414439424 + 12576789826129 = 3014368^2 + 3546377^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663204265553 - 2⁴ = 21663204265537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21663204265559) 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, 1645883426 + ... + 1645896587.

It is an arithmetic number, because the mean of its divisors is an integer number (5416624013037).

Almost surely, 2^{21663204265553} is an apocalyptic number.

It is an amenable number.

21663204265553 is a deficient number, since it is larger than the sum of its proper divisors (3291786595).

21663204265553 is an equidigital number, since it uses as much as digits as its factorization.

21663204265553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3291786594.

The product of its (nonzero) digits is 7776000, while the sum is 50.

The spelling of 21663204265553 in words is "twenty-one trillion, six hundred sixty-three billion, two hundred four million, two hundred sixty-five thousand, five hundred fifty-three".