1561491 has 16 divisors (see below), whose sum is σ = 2334720. Its totient is φ = 1031400.

The previous prime is 1561463. The next prime is 1561499. The reversal of 1561491 is 1941651.

It is not a de Polignac number, because 1561491 - 2¹¹ = 1559443 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (1561499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3886 + ... + 4268.

It is an arithmetic number, because the mean of its divisors is an integer number (145920).

2^1561491 is an apocalyptic number.

1561491 is a deficient number, since it is larger than the sum of its proper divisors (773229).

1561491 is a wasteful number, since it uses less digits than its factorization.

1561491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 543 (or 537 counting only the distinct ones).

The product of its digits is 1080, while the sum is 27.

The square root of 1561491 is about 1249.5963348218. The cubic root of 1561491 is about 116.0147375251.

The spelling of 1561491 in words is "one million, five hundred sixty-one thousand, four hundred ninety-one".