765040021 has 2 divisors, whose sum is σ = 765040022. Its totient is φ = 765040020.

The previous prime is 765040013. The next prime is 765040027. The reversal of 765040021 is 120040567.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 467856900 + 297183121 = 21630^2 + 17239^2 .

It is a cyclic number.

It is not a de Polignac number, because 765040021 - 2³ = 765040013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (765040027) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 382520010 + 382520011.

It is an arithmetic number, because the mean of its divisors is an integer number (382520011).

Almost surely, 2^765040021 is an apocalyptic number.

It is an amenable number.

765040021 is a deficient number, since it is larger than the sum of its proper divisors (1).

765040021 is an equidigital number, since it uses as much as digits as its factorization.

765040021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 765040021 is about 27659.3568435710. The cubic root of 765040021 is about 914.5933758150.

Adding to 765040021 its reverse (120040567), we get a palindrome (885080588).

The spelling of 765040021 in words is "seven hundred sixty-five million, forty thousand, twenty-one".