1991058901 has 4 divisors (see below), whose sum is σ = 2144217292. Its totient is φ = 1837900512.

The previous prime is 1991058877. The next prime is 1991058943. The reversal of 1991058901 is 1098501991.

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 340587025 + 1650471876 = 18455^2 + 40626^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991058901 - 2¹¹ = 1991056853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991058301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76579176 + ... + 76579201.

It is an arithmetic number, because the mean of its divisors is an integer number (536054323).

Almost surely, 2^1991058901 is an apocalyptic number.

It is an amenable number.

1991058901 is a deficient number, since it is larger than the sum of its proper divisors (153158391).

1991058901 is a wasteful number, since it uses less digits than its factorization.

1991058901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 153158390.

The product of its (nonzero) digits is 29160, while the sum is 43.

The square root of 1991058901 is about 44621.2830496838. The cubic root of 1991058901 is about 1258.0407319469.

The spelling of 1991058901 in words is "one billion, nine hundred ninety-one million, fifty-eight thousand, nine hundred one".