645015891 has 16 divisors (see below), whose sum is σ = 941363360. Its totient is φ = 390424320.

The previous prime is 645015871. The next prime is 645015911. The reversal of 645015891 is 198510546.

It is an interprime number because it is at equal distance from previous prime (645015871) and next prime (645015911).

It is not a de Polignac number, because 645015891 - 2⁵ = 645015859 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645015821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 133186 + ... + 137943.

It is an arithmetic number, because the mean of its divisors is an integer number (58835210).

Almost surely, 2^645015891 is an apocalyptic number.

645015891 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

645015891 is a deficient number, since it is larger than the sum of its proper divisors (296347469).

645015891 is a wasteful number, since it uses less digits than its factorization.

645015891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271206.

The product of its (nonzero) digits is 43200, while the sum is 39.

The square root of 645015891 is about 25397.1630502306. The cubic root of 645015891 is about 864.0193553299.

The spelling of 645015891 in words is "six hundred forty-five million, fifteen thousand, eight hundred ninety-one".