321021990 has 96 divisors (see below), whose sum is σ = 864302400. Its totient is φ = 82605312.

The previous prime is 321021989. The next prime is 321022003. The reversal of 321021990 is 99120123.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 495847 + ... + 496493.

It is an arithmetic number, because the mean of its divisors is an integer number (9003150).

Almost surely, 2^321021990 is an apocalyptic number.

321021990 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 321021990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (432151200).

321021990 is an abundant number, since it is smaller than the sum of its proper divisors (543280410).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

321021990 is a wasteful number, since it uses less digits than its factorization.

321021990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 846 (or 843 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 321021990 is about 17917.0865377159. The cubic root of 321021990 is about 684.7177624986.

It can be divided in two parts, 3210 and 21990, that added together give a triangular number (25200 = T₂₂₄).

The spelling of 321021990 in words is "three hundred twenty-one million, twenty-one thousand, nine hundred ninety".