21720614751 has 16 divisors (see below), whose sum is σ = 35104024320. Its totient is φ = 13164008760.

The previous prime is 21720614743. The next prime is 21720614753. The reversal of 21720614751 is 15741602712.

21720614751 is a `hidden beast` number, since 2 + 17 + 20 + 614 + 7 + 5 + 1 = 666.

It is not a de Polignac number, because 21720614751 - 2³ = 21720614743 is a prime.

It is a super-2 number, since 2×21720614751² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720614753) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 36566395 + ... + 36566988.

It is an arithmetic number, because the mean of its divisors is an integer number (2194001520).

Almost surely, 2^21720614751 is an apocalyptic number.

21720614751 is a deficient number, since it is larger than the sum of its proper divisors (13383409569).

21720614751 is a wasteful number, since it uses less digits than its factorization.

21720614751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73133403 (or 73133397 counting only the distinct ones).

The product of its (nonzero) digits is 23520, while the sum is 36.

The spelling of 21720614751 in words is "twenty-one billion, seven hundred twenty million, six hundred fourteen thousand, seven hundred fifty-one".