1561551531 has 8 divisors (see below), whose sum is σ = 2084190720. Its totient is φ = 1039973352.

The previous prime is 1561551529. The next prime is 1561551533. The reversal of 1561551531 is 1351551651.

It is an interprime number because it is at equal distance from previous prime (1561551529) and next prime (1561551533).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1561551531 - 2¹ = 1561551529 is a prime.

It is a super-2 number, since 2×1561551531² = 4876886367936887922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1561551492 and 1561551501.

It is not an unprimeable number, because it can be changed into a prime (1561551533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 261811 + ... + 267708.

It is an arithmetic number, because the mean of its divisors is an integer number (260523840).

Almost surely, 2^1561551531 is an apocalyptic number.

1561551531 is a deficient number, since it is larger than the sum of its proper divisors (522639189).

1561551531 is an equidigital number, since it uses as much as digits as its factorization.

1561551531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 530505.

The product of its digits is 11250, while the sum is 33.

The square root of 1561551531 is about 39516.4716415826. The cubic root of 1561551531 is about 1160.1623660457.

The spelling of 1561551531 in words is "one billion, five hundred sixty-one million, five hundred fifty-one thousand, five hundred thirty-one".