1991396925 has 72 divisors (see below), whose sum is σ = 4253668224. Its totient is φ = 870756480.

The previous prime is 1991396923. The next prime is 1991396929. The reversal of 1991396925 is 5296931991.

It is not a de Polignac number, because 1991396925 - 2¹ = 1991396923 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991396923) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 8739 + ... + 63711.

Almost surely, 2^1991396925 is an apocalyptic number.

1991396925 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1991396925 is an abundant number, since it is smaller than the sum of its proper divisors (2262271299).

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

1991396925 is a wasteful number, since it uses less digits than its factorization.

1991396925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55019 (or 55011 counting only the distinct ones).

The product of its digits is 1180980, while the sum is 54.

The square root of 1991396925 is about 44625.0705881795. The cubic root of 1991396925 is about 1258.1119208501. Note that the first 3 decimals are identical.

It can be divided in two parts, 199 and 1396925, that added together give a square (1397124 = 1182²).

The spelling of 1991396925 in words is "one billion, nine hundred ninety-one million, three hundred ninety-six thousand, nine hundred twenty-five".