21506065664464 has 10 divisors (see below), whose sum is σ = 41668002224930. Its totient is φ = 10753032832224.

The previous prime is 21506065664453. The next prime is 21506065664467. The reversal of 21506065664464 is 46446656060512.

It can be written as a sum of positive squares in only one way, i.e., 15653575731600 + 5852489932864 = 3956460^2 + 2419192^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506065664467) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 672064551999 + ... + 672064552030.

It is an arithmetic number, because the mean of its divisors is an integer number (4166800222493).

Almost surely, 2^{21506065664464} is an apocalyptic number.

It is an amenable number.

21506065664464 is a deficient number, since it is larger than the sum of its proper divisors (20161936560466).

21506065664464 is a wasteful number, since it uses less digits than its factorization.

21506065664464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1344129104037 (or 1344129104031 counting only the distinct ones).

The product of its (nonzero) digits is 24883200, while the sum is 55.

The spelling of 21506065664464 in words is "twenty-one trillion, five hundred six billion, sixty-five million, six hundred sixty-four thousand, four hundred sixty-four".