766891981 has 8 divisors (see below), whose sum is σ = 838197504. Its totient is φ = 698496960.

The previous prime is 766891973. The next prime is 766891987. The reversal of 766891981 is 189198667.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 766891981 - 2³ = 766891973 is a prime.

It is a super-2 number, since 2×766891981² = 1176246621044208722, 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 (766891987) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 727075 + ... + 728128.

It is an arithmetic number, because the mean of its divisors is an integer number (104774688).

Almost surely, 2^766891981 is an apocalyptic number.

It is an amenable number.

766891981 is a deficient number, since it is larger than the sum of its proper divisors (71305523).

766891981 is a wasteful number, since it uses less digits than its factorization.

766891981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1455251.

The product of its digits is 1306368, while the sum is 55.

The square root of 766891981 is about 27692.8146095698. The cubic root of 766891981 is about 915.3307775182.

The spelling of 766891981 in words is "seven hundred sixty-six million, eight hundred ninety-one thousand, nine hundred eighty-one".