645404963641 has 9 divisors (see below), whose sum is σ = 659467735951. Its totient is φ = 631635988072.

The previous prime is 645404963591. The next prime is 645404963677. The reversal of 645404963641 is 146369404546.

The square root of 645404963641 is 803371.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 354888275625 + 290516688016 = 595725^2 + 538996^2 .

It is not a de Polignac number, because 645404963641 - 2³¹ = 643257479993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645404963141) 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 8 ways as a sum of consecutive naturals, for example, 37749891 + ... + 37766983.

Almost surely, 2^645404963641 is an apocalyptic number.

645404963641 is the 803371-st square number.

645404963641 is the 401686-th centered octagonal number.

It is an amenable number.

645404963641 is a deficient number, since it is larger than the sum of its proper divisors (14062772310).

645404963641 is an frugal number, since it uses more digits than its factorization.

645404963641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34280 (or 17140 counting only the distinct ones).

The product of its (nonzero) digits is 7464960, while the sum is 52.

The spelling of 645404963641 in words is "six hundred forty-five billion, four hundred four million, nine hundred sixty-three thousand, six hundred forty-one".