991820001 has 16 divisors (see below), whose sum is σ = 1400925888. Its totient is φ = 622003200.

The previous prime is 991819999. The next prime is 991820003. The reversal of 991820001 is 100028199.

It is an interprime number because it is at equal distance from previous prime (991819999) and next prime (991820003).

It is not a de Polignac number, because 991820001 - 2¹ = 991819999 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991820003) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 135721 + ... + 142841.

It is an arithmetic number, because the mean of its divisors is an integer number (87557868).

Almost surely, 2^991820001 is an apocalyptic number.

It is an amenable number.

991820001 is a deficient number, since it is larger than the sum of its proper divisors (409105887).

991820001 is a wasteful number, since it uses less digits than its factorization.

991820001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9872.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 991820001 is about 31493.1738794298. The cubic root of 991820001 is about 997.2658649854.

The spelling of 991820001 in words is "nine hundred ninety-one million, eight hundred twenty thousand, one".