2561491 has 2 divisors, whose sum is σ = 2561492. Its totient is φ = 2561490.

The previous prime is 2561431. The next prime is 2561513. The reversal of 2561491 is 1941652.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 2561491 - 2⁹ = 2560979 is a prime.

It is a super-2 number, since 2×2561491² = 13122472286162, which contains 22 as substring.

2561491 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (2561401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1280745 + 1280746.

It is an arithmetic number, because the mean of its divisors is an integer number (1280746).

2^2561491 is an apocalyptic number.

2561491 is a deficient number, since it is larger than the sum of its proper divisors (1).

2561491 is an equidigital number, since it uses as much as digits as its factorization.

2561491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 28.

The square root of 2561491 is about 1600.4658696767. The cubic root of 2561491 is about 136.8246286437.

It can be divided in two parts, 25 and 61491, that added together give a palindrome (61516).

The spelling of 2561491 in words is "two million, five hundred sixty-one thousand, four hundred ninety-one".