11991820 has 12 divisors (see below), whose sum is σ = 25182864. Its totient is φ = 4796720.

The previous prime is 11991781. The next prime is 11991839. The reversal of 11991820 is 2819911.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 299776 + ... + 299815.

It is an arithmetic number, because the mean of its divisors is an integer number (2098572).

Almost surely, 2^11991820 is an apocalyptic number.

11991820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

11991820 is an abundant number, since it is smaller than the sum of its proper divisors (13191044).

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

11991820 is a wasteful number, since it uses less digits than its factorization.

11991820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 599600 (or 599598 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 11991820 is about 3462.9207325609. The cubic root of 11991820 is about 228.8908157831.

The spelling of 11991820 in words is "eleven million, nine hundred ninety-one thousand, eight hundred twenty".