21978107377987 has 2 divisors, whose sum is σ = 21978107377988. Its totient is φ = 21978107377986.

The previous prime is 21978107377979. The next prime is 21978107378047. The reversal of 21978107377987 is 78977370187912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21978107377987 - 2³ = 21978107377979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21978107377927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10989053688993 + 10989053688994.

It is an arithmetic number, because the mean of its divisors is an integer number (10989053688994).

Almost surely, 2^{21978107377987} is an apocalyptic number.

21978107377987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21978107377987 is an equidigital number, since it uses as much as digits as its factorization.

21978107377987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 522764928, while the sum is 76.

The spelling of 21978107377987 in words is "twenty-one trillion, nine hundred seventy-eight billion, one hundred seven million, three hundred seventy-seven thousand, nine hundred eighty-seven".