645199491 has 4 divisors (see below), whose sum is σ = 860265992. Its totient is φ = 430132992.

The previous prime is 645199463. The next prime is 645199523. The reversal of 645199491 is 194991546.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 645199491 - 2¹⁴ = 645183107 is a prime.

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 645199491.

It is not an unprimeable number, because it can be changed into a prime (645199091) 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, 107533246 + ... + 107533251.

It is an arithmetic number, because the mean of its divisors is an integer number (215066498).

Almost surely, 2^645199491 is an apocalyptic number.

645199491 is a deficient number, since it is larger than the sum of its proper divisors (215066501).

645199491 is a wasteful number, since it uses less digits than its factorization.

645199491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215066500.

The product of its digits is 349920, while the sum is 48.

The square root of 645199491 is about 25400.7773699940. Note that the first 3 decimals coincide. The cubic root of 645199491 is about 864.1013269044.

The spelling of 645199491 in words is "six hundred forty-five million, one hundred ninety-nine thousand, four hundred ninety-one".