21147718761 has 64 divisors (see below), whose sum is σ = 34555315200. Its totient is φ = 12701069568.

The previous prime is 21147718741. The next prime is 21147718763. The reversal of 21147718761 is 16781774112.

It is not a de Polignac number, because 21147718761 - 2¹¹ = 21147716713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21147718763) 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, 6547695 + ... + 6550923.

It is an arithmetic number, because the mean of its divisors is an integer number (539926800).

Almost surely, 2^21147718761 is an apocalyptic number.

It is an amenable number.

21147718761 is a deficient number, since it is larger than the sum of its proper divisors (13407596439).

21147718761 is a wasteful number, since it uses less digits than its factorization.

21147718761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3695 (or 3689 counting only the distinct ones).

The product of its digits is 131712, while the sum is 45.

The spelling of 21147718761 in words is "twenty-one billion, one hundred forty-seven million, seven hundred eighteen thousand, seven hundred sixty-one".