51991820 has 12 divisors (see below), whose sum is σ = 109182864. Its totient is φ = 20796720.

The previous prime is 51991783. The next prime is 51991843. The reversal of 51991820 is 2819915.

It is a super-3 number, since 3×51991820³ (a number of 24 digits) contains 333 as substring.

It is an unprimeable number.

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, 1299776 + ... + 1299815.

It is an arithmetic number, because the mean of its divisors is an integer number (9098572).

Almost surely, 2^51991820 is an apocalyptic number.

It is an amenable number.

51991820 is an abundant number, since it is smaller than the sum of its proper divisors (57191044).

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

51991820 is a wasteful number, since it uses less digits than its factorization.

51991820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2599600 (or 2599598 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 35.

The square root of 51991820 is about 7210.5353476701. The cubic root of 51991820 is about 373.2315428982.

The spelling of 51991820 in words is "fifty-one million, nine hundred ninety-one thousand, eight hundred twenty".