1644257645 has 16 divisors (see below), whose sum is σ = 2043966960. Its totient is φ = 1268889600.

The previous prime is 1644257633. The next prime is 1644257647. The reversal of 1644257645 is 5467524461.

It can be written as a sum of positive squares in 8 ways, for example, as 43217476 + 1601040169 = 6574^2 + 40013^2 .

It is not a de Polignac number, because 1644257645 - 2⁶ = 1644257581 is a prime.

It is a super-3 number, since 3×1644257645³ (a number of 29 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 1644257596 and 1644257605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1644257647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26816 + ... + 63305.

It is an arithmetic number, because the mean of its divisors is an integer number (127747935).

Almost surely, 2^1644257645 is an apocalyptic number.

It is an amenable number.

1644257645 is a deficient number, since it is larger than the sum of its proper divisors (399709315).

1644257645 is an equidigital number, since it uses as much as digits as its factorization.

1644257645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90256.

The product of its digits is 806400, while the sum is 44.

The square root of 1644257645 is about 40549.4469136140. The cubic root of 1644257645 is about 1180.2933401234.

The spelling of 1644257645 in words is "one billion, six hundred forty-four million, two hundred fifty-seven thousand, six hundred forty-five".