21720149768 has 8 divisors (see below), whose sum is σ = 40725280830. Its totient is φ = 10860074880.

The previous prime is 21720149707. The next prime is 21720149777. The reversal of 21720149768 is 86794102712.

It can be written as a sum of positive squares in only one way, i.e., 21714380164 + 5769604 = 147358^2 + 2402^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1357509353 + ... + 1357509368.

Almost surely, 2^21720149768 is an apocalyptic number.

It is an amenable number.

21720149768 is a deficient number, since it is larger than the sum of its proper divisors (19005131062).

21720149768 is a wasteful number, since it uses less digits than its factorization.

21720149768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2715018727 (or 2715018723 counting only the distinct ones).

The product of its (nonzero) digits is 338688, while the sum is 47.

The spelling of 21720149768 in words is "twenty-one billion, seven hundred twenty million, one hundred forty-nine thousand, seven hundred sixty-eight".