764640781 has 4 divisors (see below), whose sum is σ = 764751292. Its totient is φ = 764530272.

The previous prime is 764640743. The next prime is 764640787. The reversal of 764640781 is 187046467.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 512116900 + 252523881 = 22630^2 + 15891^2 .

It is a cyclic number.

It is not a de Polignac number, because 764640781 - 2¹⁷ = 764509709 is a prime.

It is a super-2 number, since 2×764640781² = 1169351047936579922, 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 (764640787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 44130 + ... + 58963.

It is an arithmetic number, because the mean of its divisors is an integer number (191187823).

Almost surely, 2^764640781 is an apocalyptic number.

It is an amenable number.

764640781 is a deficient number, since it is larger than the sum of its proper divisors (110511).

764640781 is a wasteful number, since it uses less digits than its factorization.

764640781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110510.

The product of its (nonzero) digits is 225792, while the sum is 43.

The square root of 764640781 is about 27652.1388142039. The cubic root of 764640781 is about 914.4342530742.

The spelling of 764640781 in words is "seven hundred sixty-four million, six hundred forty thousand, seven hundred eighty-one".