21666077561655 has 24 divisors (see below), whose sum is σ = 38115049884912. Its totient is φ = 11382775075584.

The previous prime is 21666077561593. The next prime is 21666077561657. The reversal of 21666077561655 is 55616577066612.

It is not a de Polignac number, because 21666077561655 - 2⁶ = 21666077561591 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21666077561592 and 21666077561601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21666077561657) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3593044674 + ... + 3593050703.

It is an arithmetic number, because the mean of its divisors is an integer number (1588127078538).

Almost surely, 2^{21666077561655} is an apocalyptic number.

21666077561655 is a deficient number, since it is larger than the sum of its proper divisors (16448972323257).

21666077561655 is a wasteful number, since it uses less digits than its factorization.

21666077561655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7186095455 (or 7186095452 counting only the distinct ones).

The product of its (nonzero) digits is 95256000, while the sum is 63.

The spelling of 21666077561655 in words is "twenty-one trillion, six hundred sixty-six billion, seventy-seven million, five hundred sixty-one thousand, six hundred fifty-five".