921800991 has 16 divisors (see below), whose sum is σ = 1272041568. Its totient is φ = 593356800.

The previous prime is 921800987. The next prime is 921801007. The reversal of 921800991 is 199008129.

It is a happy number.

It is not a de Polignac number, because 921800991 - 2² = 921800987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (921800921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26700 + ... + 50561.

It is an arithmetic number, because the mean of its divisors is an integer number (79502598).

Almost surely, 2^921800991 is an apocalyptic number.

921800991 is a deficient number, since it is larger than the sum of its proper divisors (350240577).

921800991 is a wasteful number, since it uses less digits than its factorization.

921800991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77402.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 921800991 is about 30361.1757183413. The cubic root of 921800991 is about 973.2230588174.

The spelling of 921800991 in words is "nine hundred twenty-one million, eight hundred thousand, nine hundred ninety-one".