21621938977 has 2 divisors, whose sum is σ = 21621938978. Its totient is φ = 21621938976.

The previous prime is 21621938959. The next prime is 21621938981. The reversal of 21621938977 is 77983912612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18454950801 + 3166988176 = 135849^2 + 56276^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21621938977 is a prime.

It is a super-2 number, since 2×21621938977² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21621938917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810969488 + 10810969489.

It is an arithmetic number, because the mean of its divisors is an integer number (10810969489).

Almost surely, 2^21621938977 is an apocalyptic number.

It is an amenable number.

21621938977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621938977 is an equidigital number, since it uses as much as digits as its factorization.

21621938977 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2286144, while the sum is 55.

The spelling of 21621938977 in words is "twenty-one billion, six hundred twenty-one million, nine hundred thirty-eight thousand, nine hundred seventy-seven".