2491445981 has 4 divisors (see below), whose sum is σ = 2525575452. Its totient is φ = 2457316512.

The previous prime is 2491445977. The next prime is 2491446029. The reversal of 2491445981 is 1895441942.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1895441942 = 2 ⋅947720971.

It can be written as a sum of positive squares in 2 ways, for example, as 1894425625 + 597020356 = 43525^2 + 24434^2 .

It is a cyclic number.

It is not a de Polignac number, because 2491445981 - 2² = 2491445977 is a prime.

It is a super-2 number, since 2×2491445981² = 12414606152482104722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2491445911) 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, 17064626 + ... + 17064771.

It is an arithmetic number, because the mean of its divisors is an integer number (631393863).

Almost surely, 2^2491445981 is an apocalyptic number.

It is an amenable number.

2491445981 is a deficient number, since it is larger than the sum of its proper divisors (34129471).

2491445981 is an equidigital number, since it uses as much as digits as its factorization.

2491445981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34129470.

The product of its digits is 414720, while the sum is 47.

The square root of 2491445981 is about 49914.3865133090. The cubic root of 2491445981 is about 1355.6590941222.

The spelling of 2491445981 in words is "two billion, four hundred ninety-one million, four hundred forty-five thousand, nine hundred eighty-one".