990421021820 has 96 divisors (see below), whose sum is σ = 2184632432640. Its totient is φ = 376672193280.

The previous prime is 990421021801. The next prime is 990421021829. The reversal of 990421021820 is 28120124099.

It is a super-2 number, since 2×990421021820² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (990421021829) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 72165479 + ... + 72179201.

It is an arithmetic number, because the mean of its divisors is an integer number (22756587840).

Almost surely, 2^990421021820 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 990421021820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1092316216320).

990421021820 is an abundant number, since it is smaller than the sum of its proper divisors (1194211410820).

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

990421021820 is a wasteful number, since it uses less digits than its factorization.

990421021820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15795 (or 15793 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 38.

The spelling of 990421021820 in words is "nine hundred ninety billion, four hundred twenty-one million, twenty-one thousand, eight hundred twenty".