16561405665351 has 64 divisors (see below), whose sum is σ = 25251304243200. Its totient is φ = 10720055808000.

The previous prime is 16561405665271. The next prime is 16561405665433. The reversal of 16561405665351 is 15356650416561.

16561405665351 is a `hidden beast` number, since 1 + 6 + 5 + 6 + 1 + 40 + 5 + 66 + 535 + 1 = 666.

It is not a de Polignac number, because 16561405665351 - 2⁷ = 16561405665223 is a prime.

It is a super-2 number, since 2×16561405665351² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561405661351) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1433758026 + ... + 1433769576.

It is an arithmetic number, because the mean of its divisors is an integer number (394551628800).

Almost surely, 2^{16561405665351} is an apocalyptic number.

16561405665351 is a deficient number, since it is larger than the sum of its proper divisors (8689898577849).

16561405665351 is a wasteful number, since it uses less digits than its factorization.

16561405665351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14477 (or 14471 counting only the distinct ones).

The product of its (nonzero) digits is 9720000, while the sum is 54.

The spelling of 16561405665351 in words is "sixteen trillion, five hundred sixty-one billion, four hundred five million, six hundred sixty-five thousand, three hundred fifty-one".