21564877813 has 2 divisors, whose sum is σ = 21564877814. Its totient is φ = 21564877812.

The previous prime is 21564877793. The next prime is 21564877837. The reversal of 21564877813 is 31877846512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21537910564 + 26967249 = 146758^2 + 5193^2 .

It is a cyclic number.

It is not a de Polignac number, because 21564877813 - 2⁵ = 21564877781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21564877843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10782438906 + 10782438907.

It is an arithmetic number, because the mean of its divisors is an integer number (10782438907).

Almost surely, 2^21564877813 is an apocalyptic number.

It is an amenable number.

21564877813 is a deficient number, since it is larger than the sum of its proper divisors (1).

21564877813 is an equidigital number, since it uses as much as digits as its factorization.

21564877813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2257920, while the sum is 52.

The spelling of 21564877813 in words is "twenty-one billion, five hundred sixty-four million, eight hundred seventy-seven thousand, eight hundred thirteen".