2181991825 has 24 divisors (see below), whose sum is σ = 3067164800. Its totient is φ = 1526506560.

The previous prime is 2181991811. The next prime is 2181991841. The reversal of 2181991825 is 5281991812.

It is a happy number.

It is not a de Polignac number, because 2181991825 - 2⁵ = 2181991793 is a prime.

It is a super-2 number, since 2×2181991825² = 9522176648733661250, which contains 22 as substring.

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, 170505 + ... + 182854.

Almost surely, 2^2181991825 is an apocalyptic number.

2181991825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

2181991825 is a deficient number, since it is larger than the sum of its proper divisors (885172975).

2181991825 is a wasteful number, since it uses less digits than its factorization.

2181991825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 353401 (or 353396 counting only the distinct ones).

The product of its digits is 103680, while the sum is 46.

The square root of 2181991825 is about 46711.7953519237. The cubic root of 2181991825 is about 1297.0330414259.

The spelling of 2181991825 in words is "two billion, one hundred eighty-one million, nine hundred ninety-one thousand, eight hundred twenty-five".