21751664677 has 2 divisors, whose sum is σ = 21751664678. Its totient is φ = 21751664676.

The previous prime is 21751664617. The next prime is 21751664689. The reversal of 21751664677 is 77646615712.

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., 20040932356 + 1710732321 = 141566^2 + 41361^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21751664677 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21751664617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10875832338 + 10875832339.

It is an arithmetic number, because the mean of its divisors is an integer number (10875832339).

Almost surely, 2^21751664677 is an apocalyptic number.

It is an amenable number.

21751664677 is a deficient number, since it is larger than the sum of its proper divisors (1).

21751664677 is an equidigital number, since it uses as much as digits as its factorization.

21751664677 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2963520, while the sum is 52.

The spelling of 21751664677 in words is "twenty-one billion, seven hundred fifty-one million, six hundred sixty-four thousand, six hundred seventy-seven".