991620 has 72 divisors (see below), whose sum is σ = 3441984. Its totient is φ = 226368.

The previous prime is 991619. The next prime is 991621. The reversal of 991620 is 26199.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (991619) and next prime (991621).

It is not an unprimeable number, because it can be changed into a prime (991621) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 867 + ... + 1653.

2⁹⁹¹⁶²⁰ is an apocalyptic number.

991620 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 991620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1720992).

991620 is an abundant number, since it is smaller than the sum of its proper divisors (2450364).

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

991620 is a wasteful number, since it uses less digits than its factorization.

991620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 809 (or 804 counting only the distinct ones).

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

The square root of 991620 is about 995.8011849762. The cubic root of 991620 is about 99.7198827425.

The spelling of 991620 in words is "nine hundred ninety-one thousand, six hundred twenty".