645520157 has 4 divisors (see below), whose sum is σ = 647349180. Its totient is φ = 643691136.

The previous prime is 645520151. The next prime is 645520181. The reversal of 645520157 is 751025546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 751025546 = 2 ⋅375512773.

It can be written as a sum of positive squares in 2 ways, for example, as 203091001 + 442429156 = 14251^2 + 21034^2 .

It is a cyclic number.

It is not a de Polignac number, because 645520157 - 2¹⁸ = 645258013 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645520151) 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, 913982 + ... + 914687.

It is an arithmetic number, because the mean of its divisors is an integer number (161837295).

Almost surely, 2^645520157 is an apocalyptic number.

It is an amenable number.

645520157 is a deficient number, since it is larger than the sum of its proper divisors (1829023).

645520157 is a wasteful number, since it uses less digits than its factorization.

645520157 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1829022.

The product of its (nonzero) digits is 42000, while the sum is 35.

The square root of 645520157 is about 25407.0887155534. The cubic root of 645520157 is about 864.2444568088.

The spelling of 645520157 in words is "six hundred forty-five million, five hundred twenty thousand, one hundred fifty-seven".