1991620 has 12 divisors (see below), whose sum is σ = 4182444. Its totient is φ = 796640.

The previous prime is 1991617. The next prime is 1991623. The reversal of 1991620 is 261991.

It is an interprime number because it is at equal distance from previous prime (1991617) and next prime (1991623).

It can be written as a sum of positive squares in 2 ways, for example, as 1258884 + 732736 = 1122^2 + 856^2 .

It is not an unprimeable number, because it can be changed into a prime (1991623) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 49771 + ... + 49810.

It is an arithmetic number, because the mean of its divisors is an integer number (348537).

2^1991620 is an apocalyptic number.

1991620 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1991620 is an abundant number, since it is smaller than the sum of its proper divisors (2190824).

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

1991620 is a wasteful number, since it uses less digits than its factorization.

1991620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99590 (or 99588 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 1991620 is about 1411.2476749317. The cubic root of 1991620 is about 125.8158896725.

The spelling of 1991620 in words is "one million, nine hundred ninety-one thousand, six hundred twenty".