645350661 has 6 divisors (see below), whose sum is σ = 932173190. Its totient is φ = 430233768.

The previous prime is 645350639. The next prime is 645350663. The reversal of 645350661 is 166053546.

645350661 is a `hidden beast` number, since 64 + 535 + 0 + 6 + 61 = 666.

It can be written as a sum of positive squares in only one way, i.e., 622253025 + 23097636 = 24945^2 + 4806^2 .

It is not a de Polignac number, because 645350661 - 2⁶ = 645350597 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645350663) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35852806 + ... + 35852823.

Almost surely, 2^645350661 is an apocalyptic number.

It is an amenable number.

645350661 is a deficient number, since it is larger than the sum of its proper divisors (286822529).

645350661 is a wasteful number, since it uses less digits than its factorization.

645350661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71705635 (or 71705632 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 36.

The square root of 645350661 is about 25403.7528920433. The cubic root of 645350661 is about 864.1688078406.

The spelling of 645350661 in words is "six hundred forty-five million, three hundred fifty thousand, six hundred sixty-one".