1644257641 has 4 divisors (see below), whose sum is σ = 1770739012. Its totient is φ = 1517776272.

The previous prime is 1644257633. The next prime is 1644257647. The reversal of 1644257641 is 1467524461.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 362331225 + 1281926416 = 19035^2 + 35804^2 .

It is a cyclic number.

It is not a de Polignac number, because 1644257641 - 2³ = 1644257633 is a prime.

It is a super-3 number, since 3×1644257641³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1644257594 and 1644257603.

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

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63240666 + ... + 63240691.

It is an arithmetic number, because the mean of its divisors is an integer number (442684753).

Almost surely, 2^1644257641 is an apocalyptic number.

It is an amenable number.

1644257641 is a deficient number, since it is larger than the sum of its proper divisors (126481371).

1644257641 is a wasteful number, since it uses less digits than its factorization.

1644257641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126481370.

The product of its digits is 161280, while the sum is 40.

The square root of 1644257641 is about 40549.4468642915. The cubic root of 1644257641 is about 1180.2933391663.

The spelling of 1644257641 in words is "one billion, six hundred forty-four million, two hundred fifty-seven thousand, six hundred forty-one".