21766564999 has 2 divisors, whose sum is σ = 21766565000. Its totient is φ = 21766564998.

The previous prime is 21766564973. The next prime is 21766565011. The reversal of 21766564999 is 99946566712.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21766564999 - 2³³ = 13176630407 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21766564999.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21766564909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10883282499 + 10883282500.

It is an arithmetic number, because the mean of its divisors is an integer number (10883282500).

Almost surely, 2^21766564999 is an apocalyptic number.

21766564999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21766564999 is an equidigital number, since it uses as much as digits as its factorization.

21766564999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 44089920, while the sum is 64.

The spelling of 21766564999 in words is "twenty-one billion, seven hundred sixty-six million, five hundred sixty-four thousand, nine hundred ninety-nine".