1561437335921 has 2 divisors, whose sum is σ = 1561437335922. Its totient is φ = 1561437335920.

The previous prime is 1561437335879. The next prime is 1561437335977. The reversal of 1561437335921 is 1295337341651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1500230575921 + 61206760000 = 1224839^2 + 247400^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561437335921 - 2³⁴ = 1544257466737 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1561437335921.

It is not a weakly prime, because it can be changed into another prime (1561437335981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780718667960 + 780718667961.

It is an arithmetic number, because the mean of its divisors is an integer number (780718667961).

Almost surely, 2^{1561437335921} is an apocalyptic number.

It is an amenable number.

1561437335921 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561437335921 is an equidigital number, since it uses as much as digits as its factorization.

1561437335921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2041200, while the sum is 50.

The spelling of 1561437335921 in words is "one trillion, five hundred sixty-one billion, four hundred thirty-seven million, three hundred thirty-five thousand, nine hundred twenty-one".