21497785577 has 2 divisors, whose sum is σ = 21497785578. Its totient is φ = 21497785576.

The previous prime is 21497785501. The next prime is 21497785583. The reversal of 21497785577 is 77558779412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20015458576 + 1482327001 = 141476^2 + 38501^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21497785577 is a prime.

It is not a weakly prime, because it can be changed into another prime (21497784577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10748892788 + 10748892789.

It is an arithmetic number, because the mean of its divisors is an integer number (10748892789).

Almost surely, 2^21497785577 is an apocalyptic number.

It is an amenable number.

21497785577 is a deficient number, since it is larger than the sum of its proper divisors (1).

21497785577 is an equidigital number, since it uses as much as digits as its factorization.

21497785577 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34574400, while the sum is 62.

The spelling of 21497785577 in words is "twenty-one billion, four hundred ninety-seven million, seven hundred eighty-five thousand, five hundred seventy-seven".