645904168090 has 16 divisors (see below), whose sum is σ = 1162659254760. Its totient is φ = 258354611200.

The previous prime is 645904168087. The next prime is 645904168099. The reversal of 645904168090 is 90861409546.

It is a happy number.

645904168090 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 306007006041 + 339897162049 = 553179^2 + 583007^2 .

It is not an unprimeable number, because it can be changed into a prime (645904168099) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 489211 + ... + 1237390.

Almost surely, 2^645904168090 is an apocalyptic number.

645904168090 is a deficient number, since it is larger than the sum of its proper divisors (516755086670).

645904168090 is a wasteful number, since it uses less digits than its factorization.

645904168090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1764017.

The product of its (nonzero) digits is 1866240, while the sum is 52.

The spelling of 645904168090 in words is "six hundred forty-five billion, nine hundred four million, one hundred sixty-eight thousand, ninety".