11981820 has 24 divisors (see below), whose sum is σ = 33549264. Its totient is φ = 3195136.

The previous prime is 11981813. The next prime is 11981831. The reversal of 11981820 is 2818911.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 99789 + ... + 99908.

It is an arithmetic number, because the mean of its divisors is an integer number (1397886).

Almost surely, 2^11981820 is an apocalyptic number.

11981820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

11981820 is an abundant number, since it is smaller than the sum of its proper divisors (21567444).

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

11981820 is a wasteful number, since it uses less digits than its factorization.

11981820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199709 (or 199707 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 11981820 is about 3461.4765635491. The cubic root of 11981820 is about 228.8271739368.

The spelling of 11981820 in words is "eleven million, nine hundred eighty-one thousand, eight hundred twenty".