2491781 has 4 divisors (see below), whose sum is σ = 2507232. Its totient is φ = 2476332.

The previous prime is 2491777. The next prime is 2491787. The reversal of 2491781 is 1871942.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1871942 = 2 ⋅935971.

It is a cyclic number.

It is not a de Polignac number, because 2491781 - 2² = 2491777 is a prime.

It is a super-2 number, since 2×2491781² = 12417945103922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2491787) 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, 7481 + ... + 7806.

It is an arithmetic number, because the mean of its divisors is an integer number (626808).

2^2491781 is an apocalyptic number.

It is an amenable number.

2491781 is a deficient number, since it is larger than the sum of its proper divisors (15451).

2491781 is a wasteful number, since it uses less digits than its factorization.

2491781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15450.

The product of its digits is 4032, while the sum is 32.

The square root of 2491781 is about 1578.5376143760. The cubic root of 2491781 is about 135.5719855517.

The spelling of 2491781 in words is "two million, four hundred ninety-one thousand, seven hundred eighty-one".