21786720867 has 6 divisors (see below), whose sum is σ = 31469707932. Its totient is φ = 14524480572.

The previous prime is 21786720773. The next prime is 21786720871. The reversal of 21786720867 is 76802768712.

It is a happy number.

It is not a de Polignac number, because 21786720867 - 2⁸ = 21786720611 is a prime.

It is a super-2 number, since 2×21786720867² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21786720877) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1210373373 + ... + 1210373390.

It is an arithmetic number, because the mean of its divisors is an integer number (5244951322).

Almost surely, 2^21786720867 is an apocalyptic number.

21786720867 is a deficient number, since it is larger than the sum of its proper divisors (9682987065).

21786720867 is a wasteful number, since it uses less digits than its factorization.

21786720867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2420746769 (or 2420746766 counting only the distinct ones).

The product of its (nonzero) digits is 3161088, while the sum is 54.

The spelling of 21786720867 in words is "twenty-one billion, seven hundred eighty-six million, seven hundred twenty thousand, eight hundred sixty-seven".