766511821 has 4 divisors (see below), whose sum is σ = 766569600. Its totient is φ = 766454044.

The previous prime is 766511791. The next prime is 766511833. The reversal of 766511821 is 128115667.

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, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 128115667 = 809 ⋅158363.

It is a cyclic number.

It is not a de Polignac number, because 766511821 - 2⁷ = 766511693 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 (766511881) 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, 2070 + ... + 39208.

It is an arithmetic number, because the mean of its divisors is an integer number (191642400).

Almost surely, 2^766511821 is an apocalyptic number.

It is an amenable number.

766511821 is a deficient number, since it is larger than the sum of its proper divisors (57779).

766511821 is a wasteful number, since it uses less digits than its factorization.

766511821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57778.

The product of its digits is 20160, while the sum is 37.

The square root of 766511821 is about 27685.9498843728. The cubic root of 766511821 is about 915.1795047309.

The spelling of 766511821 in words is "seven hundred sixty-six million, five hundred eleven thousand, eight hundred twenty-one".