21660553145465 has 16 divisors (see below), whose sum is σ = 27992807010000. Its totient is φ = 15995081079552.

The previous prime is 21660553145447. The next prime is 21660553145549. The reversal of 21660553145465 is 56454135506612.

It can be written as a sum of positive squares in 8 ways, for example, as 380821049449 + 21279732096016 = 617107^2 + 4612996^2 .

It is a cyclic number.

It is not a de Polignac number, because 21660553145465 - 2¹² = 21660553141369 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1608110 + ... + 6775479.

It is an arithmetic number, because the mean of its divisors is an integer number (1749550438125).

Almost surely, 2^{21660553145465} is an apocalyptic number.

It is an amenable number.

21660553145465 is a deficient number, since it is larger than the sum of its proper divisors (6332253864535).

21660553145465 is a wasteful number, since it uses less digits than its factorization.

21660553145465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8423356.

The product of its (nonzero) digits is 12960000, while the sum is 53.

The spelling of 21660553145465 in words is "twenty-one trillion, six hundred sixty billion, five hundred fifty-three million, one hundred forty-five thousand, four hundred sixty-five".