766691521 has 4 divisors (see below), whose sum is σ = 774135232. Its totient is φ = 759247812.

The previous prime is 766691509. The next prime is 766691533. The reversal of 766691521 is 125196667.

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 an interprime number because it is at equal distance from previous prime (766691509) and next prime (766691533).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-766691521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (766691581) 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, 3721701 + ... + 3721906.

It is an arithmetic number, because the mean of its divisors is an integer number (193533808).

Almost surely, 2^766691521 is an apocalyptic number.

It is an amenable number.

766691521 is a deficient number, since it is larger than the sum of its proper divisors (7443711).

766691521 is a wasteful number, since it uses less digits than its factorization.

766691521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7443710.

The product of its digits is 136080, while the sum is 43.

The square root of 766691521 is about 27689.1950226076. The cubic root of 766691521 is about 915.2510169600.

The spelling of 766691521 in words is "seven hundred sixty-six million, six hundred ninety-one thousand, five hundred twenty-one".