645406169 has 4 divisors (see below), whose sum is σ = 655986660. Its totient is φ = 634825680.

The previous prime is 645406147. The next prime is 645406187. The reversal of 645406169 is 961604546.

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 30118144 + 615288025 = 5488^2 + 24805^2 .

It is a cyclic number.

It is not a de Polignac number, because 645406169 - 2²⁴ = 628628953 is a prime.

It is a super-2 number, since 2×645406169² = 833098245966513122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645406129) 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, 5290154 + ... + 5290275.

It is an arithmetic number, because the mean of its divisors is an integer number (163996665).

Almost surely, 2^645406169 is an apocalyptic number.

It is an amenable number.

645406169 is a deficient number, since it is larger than the sum of its proper divisors (10580491).

645406169 is a wasteful number, since it uses less digits than its factorization.

645406169 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10580490.

The product of its (nonzero) digits is 155520, while the sum is 41.

The square root of 645406169 is about 25404.8453842963. The cubic root of 645406169 is about 864.1935834703.

The spelling of 645406169 in words is "six hundred forty-five million, four hundred six thousand, one hundred sixty-nine".