1561831 has 4 divisors (see below), whose sum is σ = 1565872. Its totient is φ = 1557792.

The previous prime is 1561829. The next prime is 1561883. The reversal of 1561831 is 1381651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1381651 = 113 ⋅12227.

It is a cyclic number.

It is not a de Polignac number, because 1561831 - 2¹ = 1561829 is a prime.

It is a super-2 number, since 2×1561831² = 4878632145122, 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 = 1561796 and 1561805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561801) 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, 1371 + ... + 2236.

It is an arithmetic number, because the mean of its divisors is an integer number (391468).

2^1561831 is an apocalyptic number.

1561831 is a deficient number, since it is larger than the sum of its proper divisors (4041).

1561831 is an equidigital number, since it uses as much as digits as its factorization.

1561831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4040.

The product of its digits is 720, while the sum is 25.

The square root of 1561831 is about 1249.7323713500. The cubic root of 1561831 is about 116.0231572872.

The spelling of 1561831 in words is "one million, five hundred sixty-one thousand, eight hundred thirty-one".