21247731577 has 2 divisors, whose sum is σ = 21247731578. Its totient is φ = 21247731576.

The previous prime is 21247731529. The next prime is 21247731611. The reversal of 21247731577 is 77513774212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16357386816 + 4890344761 = 127896^2 + 69931^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21247731577 is a prime.

It is not a weakly prime, because it can be changed into another prime (21247711577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10623865788 + 10623865789.

It is an arithmetic number, because the mean of its divisors is an integer number (10623865789).

Almost surely, 2^21247731577 is an apocalyptic number.

It is an amenable number.

21247731577 is a deficient number, since it is larger than the sum of its proper divisors (1).

21247731577 is an equidigital number, since it uses as much as digits as its factorization.

21247731577 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576240, while the sum is 46.

The spelling of 21247731577 in words is "twenty-one billion, two hundred forty-seven million, seven hundred thirty-one thousand, five hundred seventy-seven".