644972545 has 24 divisors (see below), whose sum is σ = 905592744. Its totient is φ = 439681536.

The previous prime is 644972519. The next prime is 644972563. The reversal of 644972545 is 545279446.

It is a Cunningham number, because it is equal to 864³+1.

It can be written as a sum of positive squares in 4 ways, for example, as 305270784 + 339701761 = 17472^2 + 18431^2 .

It is not a de Polignac number, because 644972545 - 2⁹ = 644972033 is a prime.

It is a Smith number, since the sum of its digits (46) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 644972495 and 644972504.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34777 + ... + 49993.

It is an arithmetic number, because the mean of its divisors is an integer number (37733031).

It is a Proth number, since it is equal to 19683 ⋅ 2¹⁵ + 1 and 19683 < 2¹⁵.

Almost surely, 2^644972545 is an apocalyptic number.

It is an amenable number.

644972545 is a deficient number, since it is larger than the sum of its proper divisors (260620199).

644972545 is a wasteful number, since it uses less digits than its factorization.

644972545 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15409 (or 15402 counting only the distinct ones).

The product of its digits is 1209600, while the sum is 46.

The square root of 644972545 is about 25396.3096728639. The cubic root of 644972545 is about 864.0000004465. Note that the first 6 decimals are identical.

The spelling of 644972545 in words is "six hundred forty-four million, nine hundred seventy-two thousand, five hundred forty-five".