21978107377991 has 16 divisors (see below), whose sum is σ = 22242533068800. Its totient is φ = 21714075839808.

The previous prime is 21978107377987. The next prime is 21978107378047. The reversal of 21978107377991 is 19977370187912.

It is a cyclic number.

It is not a de Polignac number, because 21978107377991 - 2² = 21978107377987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21978107373991) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 880273790 + ... + 880298756.

It is an arithmetic number, because the mean of its divisors is an integer number (1390158316800).

Almost surely, 2^{21978107377991} is an apocalyptic number.

21978107377991 is a deficient number, since it is larger than the sum of its proper divisors (264425690809).

21978107377991 is a wasteful number, since it uses less digits than its factorization.

21978107377991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32438.

The product of its (nonzero) digits is 84015792, while the sum is 71.

The spelling of 21978107377991 in words is "twenty-one trillion, nine hundred seventy-eight billion, one hundred seven million, three hundred seventy-seven thousand, nine hundred ninety-one".