21557172149 has 2 divisors, whose sum is σ = 21557172150. Its totient is φ = 21557172148.

The previous prime is 21557172137. The next prime is 21557172179. The reversal of 21557172149 is 94127175512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14398320049 + 7158852100 = 119993^2 + 84610^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21557172149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21557172179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10778586074 + 10778586075.

It is an arithmetic number, because the mean of its divisors is an integer number (10778586075).

Almost surely, 2^21557172149 is an apocalyptic number.

It is an amenable number.

21557172149 is a deficient number, since it is larger than the sum of its proper divisors (1).

21557172149 is an equidigital number, since it uses as much as digits as its factorization.

21557172149 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 176400, while the sum is 44.

The spelling of 21557172149 in words is "twenty-one billion, five hundred fifty-seven million, one hundred seventy-two thousand, one hundred forty-nine".