1643961825 has 144 divisors (see below), whose sum is σ = 3386824896. Its totient is φ = 783820800.

The previous prime is 1643961811. The next prime is 1643961857. The reversal of 1643961825 is 5281693461.

1643961825 is a `hidden beast` number, since 1 + 6 + 4 + 3 + 9 + 618 + 25 = 666.

It is not a de Polignac number, because 1643961825 - 2⁵ = 1643961793 is a prime.

It is a super-2 number, since 2×1643961825² = 5405220964114661250, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 4878057 + ... + 4878393.

Almost surely, 2^1643961825 is an apocalyptic number.

1643961825 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1643961825 is an abundant number, since it is smaller than the sum of its proper divisors (1742863071).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1643961825 is a wasteful number, since it uses less digits than its factorization.

1643961825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 446 (or 429 counting only the distinct ones).

The product of its digits is 311040, while the sum is 45.

The square root of 1643961825 is about 40545.7991042229. The cubic root of 1643961825 is about 1180.2225533019. Note that the first 3 decimals are identical.

The spelling of 1643961825 in words is "one billion, six hundred forty-three million, nine hundred sixty-one thousand, eight hundred twenty-five".