991021880 has 32 divisors (see below), whose sum is σ = 2232703440. Its totient is φ = 395892480.

The previous prime is 991021873. The next prime is 991021883. The reversal of 991021880 is 88120199.

991021880 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991021883) 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, 15740 + ... + 47220.

Almost surely, 2^991021880 is an apocalyptic number.

It is a pronic number, being equal to 31480×31481.

It is an amenable number.

991021880 is an abundant number, since it is smaller than the sum of its proper divisors (1241681560).

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

991021880 is a wasteful number, since it uses less digits than its factorization.

991021880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32279 (or 32275 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 38.

The square root of 991021880 is about 31480.4999960293. The cubic root of 991021880 is about 996.9982920984.

The spelling of 991021880 in words is "nine hundred ninety-one million, twenty-one thousand, eight hundred eighty".