991020001 has 4 divisors (see below), whose sum is σ = 991162900. Its totient is φ = 990877104.

The previous prime is 991019923. The next prime is 991020007. The reversal of 991020001 is 100020199.

991020001 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 760435776 + 230584225 = 27576^2 + 15185^2 .

It is a cyclic number.

It is not a de Polignac number, because 991020001 - 2¹⁵ = 990987233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991020007) 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, 60486 + ... + 75103.

It is an arithmetic number, because the mean of its divisors is an integer number (247790725).

Almost surely, 2^991020001 is an apocalyptic number.

It is an amenable number.

991020001 is a deficient number, since it is larger than the sum of its proper divisors (142899).

991020001 is a wasteful number, since it uses less digits than its factorization.

991020001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142898.

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 991020001 is about 31480.4701521435. The cubic root of 991020001 is about 996.9976619875.

It can be divided in two parts, 99 and 1020001, that added together give a square (1020100 = 1010²).

The spelling of 991020001 in words is "nine hundred ninety-one million, twenty thousand, one".