21557172137 has 2 divisors, whose sum is σ = 21557172138. Its totient is φ = 21557172136.

The previous prime is 21557172107. The next prime is 21557172149. The reversal of 21557172137 is 73127175512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19397804176 + 2159367961 = 139276^2 + 46469^2 .

It is a cyclic number.

It is not a de Polignac number, because 21557172137 - 2¹⁶ = 21557106601 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21557172094 and 21557172103.

It is not a weakly prime, because it can be changed into another prime (21557172107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10778586068 + 10778586069.

It is an arithmetic number, because the mean of its divisors is an integer number (10778586069).

Almost surely, 2^21557172137 is an apocalyptic number.

It is an amenable number.

21557172137 is a deficient number, since it is larger than the sum of its proper divisors (1).

21557172137 is an equidigital number, since it uses as much as digits as its factorization.

21557172137 is an evil number, because the sum of its binary digits is even.

The product of its digits is 102900, while the sum is 41.

The spelling of 21557172137 in words is "twenty-one billion, five hundred fifty-seven million, one hundred seventy-two thousand, one hundred thirty-seven".