21999715987 has 2 divisors, whose sum is σ = 21999715988. Its totient is φ = 21999715986.

The previous prime is 21999715979. The next prime is 21999716009. The reversal of 21999715987 is 78951799912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21999715987 - 2³ = 21999715979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21999715937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10999857993 + 10999857994.

It is an arithmetic number, because the mean of its divisors is an integer number (10999857994).

Almost surely, 2^21999715987 is an apocalyptic number.

21999715987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21999715987 is an equidigital number, since it uses as much as digits as its factorization.

21999715987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 25719120, while the sum is 67.

The spelling of 21999715987 in words is "twenty-one billion, nine hundred ninety-nine million, seven hundred fifteen thousand, nine hundred eighty-seven".