645772769 has 4 divisors (see below), whose sum is σ = 645917844. Its totient is φ = 645627696.

The previous prime is 645772669. The next prime is 645772793. The reversal of 645772769 is 967277546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 967277546 = 2 ⋅483638773.

It can be written as a sum of positive squares in 2 ways, for example, as 47334400 + 598438369 = 6880^2 + 24463^2 .

It is a cyclic number.

It is not a de Polignac number, because 645772769 - 2²⁰ = 644724193 is a prime.

It is a super-2 number, since 2×645772769² = 834044938363854722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 645772769.

It is not an unprimeable number, because it can be changed into a prime (645772469) 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, 65642 + ... + 74835.

It is an arithmetic number, because the mean of its divisors is an integer number (161479461).

Almost surely, 2^645772769 is an apocalyptic number.

It is an amenable number.

645772769 is a deficient number, since it is larger than the sum of its proper divisors (145075).

645772769 is a wasteful number, since it uses less digits than its factorization.

645772769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145074.

The product of its digits is 4445280, while the sum is 53.

The square root of 645772769 is about 25412.0595190551. The cubic root of 645772769 is about 864.3571773005.

The spelling of 645772769 in words is "six hundred forty-five million, seven hundred seventy-two thousand, seven hundred sixty-nine".