1581491 has 4 divisors (see below), whose sum is σ = 1624272. Its totient is φ = 1538712.

The previous prime is 1581487. The next prime is 1581499. The reversal of 1581491 is 1941851.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1581491 - 2² = 1581487 is a prime.

It is a super-2 number, since 2×1581491² = 5002227566162, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1581499) 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, 21335 + ... + 21408.

It is an arithmetic number, because the mean of its divisors is an integer number (406068).

2^1581491 is an apocalyptic number.

1581491 is a deficient number, since it is larger than the sum of its proper divisors (42781).

1581491 is an equidigital number, since it uses as much as digits as its factorization.

1581491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42780.

The product of its digits is 1440, while the sum is 29.

The square root of 1581491 is about 1257.5734570990. The cubic root of 1581491 is about 116.5079538001.

The spelling of 1581491 in words is "one million, five hundred eighty-one thousand, four hundred ninety-one".