21456661655 has 48 divisors (see below), whose sum is σ = 30458695680. Its totient is φ = 14384073600.

The previous prime is 21456661649. The next prime is 21456661661. The reversal of 21456661655 is 55616665412.

It is an interprime number because it is at equal distance from previous prime (21456661649) and next prime (21456661661).

It is not a de Polignac number, because 21456661655 - 2¹⁴ = 21456645271 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 9582026 + ... + 9584264.

It is an arithmetic number, because the mean of its divisors is an integer number (634556160).

Almost surely, 2^21456661655 is an apocalyptic number.

21456661655 is a deficient number, since it is larger than the sum of its proper divisors (9002034025).

21456661655 is a wasteful number, since it uses less digits than its factorization.

21456661655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3312 (or 3299 counting only the distinct ones).

The product of its digits is 1296000, while the sum is 47.

The spelling of 21456661655 in words is "twenty-one billion, four hundred fifty-six million, six hundred sixty-one thousand, six hundred fifty-five".