645131849 has 4 divisors (see below), whose sum is σ = 645193680. Its totient is φ = 645070020.

The previous prime is 645131821. The next prime is 645131891. The reversal of 645131849 is 948131546.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 645131849 - 2¹⁶ = 645066313 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645131549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10979 + ... + 37560.

It is an arithmetic number, because the mean of its divisors is an integer number (161298420).

Almost surely, 2^645131849 is an apocalyptic number.

It is an amenable number.

645131849 is a deficient number, since it is larger than the sum of its proper divisors (61831).

645131849 is a wasteful number, since it uses less digits than its factorization.

645131849 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61830.

The product of its digits is 103680, while the sum is 41.

The square root of 645131849 is about 25399.4458404116. The cubic root of 645131849 is about 864.0711287071.

The spelling of 645131849 in words is "six hundred forty-five million, one hundred thirty-one thousand, eight hundred forty-nine".