1561621521137 has 2 divisors, whose sum is σ = 1561621521138. Its totient is φ = 1561621521136.

The previous prime is 1561621521013. The next prime is 1561621521157. The reversal of 1561621521137 is 7311251261651.

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., 971330484721 + 590291036416 = 985561^2 + 768304^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561621521137 - 2²⁰ = 1561620472561 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1561621521094 and 1561621521103.

It is not a weakly prime, because it can be changed into another prime (1561621521157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780810760568 + 780810760569.

It is an arithmetic number, because the mean of its divisors is an integer number (780810760569).

Almost surely, 2^{1561621521137} is an apocalyptic number.

It is an amenable number.

1561621521137 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561621521137 is an equidigital number, since it uses as much as digits as its factorization.

1561621521137 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75600, while the sum is 41.

Adding to 1561621521137 its reverse (7311251261651), we get a palindrome (8872872782788).

The spelling of 1561621521137 in words is "one trillion, five hundred sixty-one billion, six hundred twenty-one million, five hundred twenty-one thousand, one hundred thirty-seven".