21977395217 has 2 divisors, whose sum is σ = 21977395218. Its totient is φ = 21977395216.

The previous prime is 21977395147. The next prime is 21977395277. The reversal of 21977395217 is 71259377912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21574028161 + 403367056 = 146881^2 + 20084^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21977395217 is a prime.

It is not a weakly prime, because it can be changed into another prime (21977395277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10988697608 + 10988697609.

It is an arithmetic number, because the mean of its divisors is an integer number (10988697609).

Almost surely, 2^21977395217 is an apocalyptic number.

It is an amenable number.

21977395217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21977395217 is an equidigital number, since it uses as much as digits as its factorization.

21977395217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1666980, while the sum is 53.

The spelling of 21977395217 in words is "twenty-one billion, nine hundred seventy-seven million, three hundred ninety-five thousand, two hundred seventeen".