21005615601 has 16 divisors (see below), whose sum is σ = 31166536320. Its totient is φ = 13982546160.

The previous prime is 21005615503. The next prime is 21005615621. The reversal of 21005615601 is 10651650012.

It is a happy number.

21005615601 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 56 + 1 + 5 + 601 = 666.

It is not a de Polignac number, because 21005615601 - 2⁷ = 21005615473 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21005615621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 570645 + ... + 606338.

It is an arithmetic number, because the mean of its divisors is an integer number (1947908520).

Almost surely, 2^21005615601 is an apocalyptic number.

It is an amenable number.

21005615601 is a deficient number, since it is larger than the sum of its proper divisors (10160920719).

21005615601 is a wasteful number, since it uses less digits than its factorization.

21005615601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1177653 (or 1177647 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

The spelling of 21005615601 in words is "twenty-one billion, five million, six hundred fifteen thousand, six hundred one".