7781981 has 4 divisors (see below), whose sum is σ = 8120352. Its totient is φ = 7443612.

The previous prime is 7781957. The next prime is 7781987. The reversal of 7781981 is 1891877.

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 a de Polignac number, because none of the positive numbers 2^k-7781981 is a prime.

It is a super-2 number, since 2×7781981² = 121118456568722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7781987) 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, 169151 + ... + 169196.

It is an arithmetic number, because the mean of its divisors is an integer number (2030088).

Almost surely, 2^7781981 is an apocalyptic number.

It is an amenable number.

7781981 is a deficient number, since it is larger than the sum of its proper divisors (338371).

7781981 is a wasteful number, since it uses less digits than its factorization.

7781981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338370.

The product of its digits is 28224, while the sum is 41.

The square root of 7781981 is about 2789.6202250486. The cubic root of 7781981 is about 198.1664162240.

The spelling of 7781981 in words is "seven million, seven hundred eighty-one thousand, nine hundred eighty-one".