991521803 has 8 divisors (see below), whose sum is σ = 1029019680. Its totient is φ = 954244480.

The previous prime is 991521799. The next prime is 991521829. The reversal of 991521803 is 308125199.

991521803 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 991521803 - 2² = 991521799 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991521833) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45950 + ... + 63987.

It is an arithmetic number, because the mean of its divisors is an integer number (128627460).

Almost surely, 2^991521803 is an apocalyptic number.

991521803 is a deficient number, since it is larger than the sum of its proper divisors (37497877).

991521803 is a wasteful number, since it uses less digits than its factorization.

991521803 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110277.

The product of its (nonzero) digits is 19440, while the sum is 38.

The square root of 991521803 is about 31488.4391959970. The cubic root of 991521803 is about 997.1659098542.

The spelling of 991521803 in words is "nine hundred ninety-one million, five hundred twenty-one thousand, eight hundred three".