2491765621 has 4 divisors (see below), whose sum is σ = 2622911200. Its totient is φ = 2360620044.

The previous prime is 2491765613. The next prime is 2491765631. The reversal of 2491765621 is 1265671942.

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.

It is a cyclic number.

It is not a de Polignac number, because 2491765621 - 2³ = 2491765613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2491765631) 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, 65572761 + ... + 65572798.

It is an arithmetic number, because the mean of its divisors is an integer number (655727800).

Almost surely, 2^2491765621 is an apocalyptic number.

It is an amenable number.

2491765621 is a deficient number, since it is larger than the sum of its proper divisors (131145579).

2491765621 is a wasteful number, since it uses less digits than its factorization.

2491765621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131145578.

The product of its digits is 181440, while the sum is 43.

The square root of 2491765621 is about 49917.5882931057. The cubic root of 2491765621 is about 1355.7170663930.

The spelling of 2491765621 in words is "two billion, four hundred ninety-one million, seven hundred sixty-five thousand, six hundred twenty-one".