1561505231 has 32 divisors (see below), whose sum is σ = 1868160000. Its totient is φ = 1286513280.

The previous prime is 1561505227. The next prime is 1561505263. The reversal of 1561505231 is 1325051651.

It is not a de Polignac number, because 1561505231 - 2² = 1561505227 is a prime.

It is a super-2 number, since 2×1561505231² = 4876597172880726722, 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 = 1561505194 and 1561505203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561505221) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3129020 + ... + 3129518.

It is an arithmetic number, because the mean of its divisors is an integer number (58380000).

Almost surely, 2^1561505231 is an apocalyptic number.

1561505231 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1561505231 is a deficient number, since it is larger than the sum of its proper divisors (306654769).

1561505231 is a wasteful number, since it uses less digits than its factorization.

1561505231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 879.

The product of its (nonzero) digits is 4500, while the sum is 29.

The square root of 1561505231 is about 39515.8858055846. The cubic root of 1561505231 is about 1160.1508996617.

Adding to 1561505231 its reverse (1325051651), we get a palindrome (2886556882).

The spelling of 1561505231 in words is "one billion, five hundred sixty-one million, five hundred five thousand, two hundred thirty-one".