1991085525 has 144 divisors (see below), whose sum is σ = 4411592640. Its totient is φ = 843955200.

The previous prime is 1991085521. The next prime is 1991085533. The reversal of 1991085525 is 5255801991.

1991085525 is a `hidden beast` number, since 1 + 9 + 91 + 0 + 8 + 552 + 5 = 666.

It is not a de Polignac number, because 1991085525 - 2² = 1991085521 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991085521) by changing a digit.

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, 609697 + ... + 612953.

It is an arithmetic number, because the mean of its divisors is an integer number (30636060).

Almost surely, 2^1991085525 is an apocalyptic number.

1991085525 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1991085525 is an abundant number, since it is smaller than the sum of its proper divisors (2420507115).

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

1991085525 is a wasteful number, since it uses less digits than its factorization.

1991085525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3316 (or 3308 counting only the distinct ones).

The product of its (nonzero) digits is 162000, while the sum is 45.

The square root of 1991085525 is about 44621.5813816588. The cubic root of 1991085525 is about 1258.0463393362.

The spelling of 1991085525 in words is "one billion, nine hundred ninety-one million, eighty-five thousand, five hundred twenty-five".