1561531 has 4 divisors (see below), whose sum is σ = 1566864. Its totient is φ = 1556200.

The previous prime is 1561529. The next prime is 1561537. The reversal of 1561531 is 1351651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1351651 = 7 ⋅193093.

It is a cyclic number.

It is not a de Polignac number, because 1561531 - 2¹ = 1561529 is a prime.

It is a super-2 number, since 2×1561531² = 4876758127922, which contains 22 as substring.

It is a Duffinian number.

It is a zygodrome in base 3.

It is not an unprimeable number, because it can be changed into a prime (1561537) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2200 + ... + 2821.

It is an arithmetic number, because the mean of its divisors is an integer number (391716).

2^1561531 is an apocalyptic number.

1561531 is a deficient number, since it is larger than the sum of its proper divisors (5333).

1561531 is an equidigital number, since it uses as much as digits as its factorization.

1561531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5332.

The product of its digits is 450, while the sum is 22.

The square root of 1561531 is about 1249.6123398879. The cubic root of 1561531 is about 116.0157281488.

The spelling of 1561531 in words is "one million, five hundred sixty-one thousand, five hundred thirty-one".