1561204631 has 20 divisors (see below), whose sum is σ = 1825871064. Its totient is φ = 1334818800.

The previous prime is 1561204591. The next prime is 1561204637. The reversal of 1561204631 is 1364021651.

It is a happy number.

It is not a de Polignac number, because 1561204631 - 2²⁶ = 1494095767 is a prime.

It is a super-2 number, since 2×1561204631² = 4874719799711692322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1561204594 and 1561204603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561204637) 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 in 19 ways as a sum of consecutive naturals, for example, 1658621 + ... + 1659561.

Almost surely, 2^1561204631 is an apocalyptic number.

1561204631 is a deficient number, since it is larger than the sum of its proper divisors (264666433).

1561204631 is an frugal number, since it uses more digits than its factorization.

1561204631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1660 (or 1639 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 1561204631 is about 39512.0820889004. The cubic root of 1561204631 is about 1160.0764493313.

The spelling of 1561204631 in words is "one billion, five hundred sixty-one million, two hundred four thousand, six hundred thirty-one".