51999981 has 8 divisors (see below), whose sum is σ = 75636384. Its totient is φ = 31515120.

The previous prime is 51999971. The next prime is 52000007. The reversal of 51999981 is 18999915.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 51999981 - 2⁷ = 51999853 is a prime.

It is a super-2 number, since 2×51999981² = 5407996048000722, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51999971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 787846 + ... + 787911.

It is an arithmetic number, because the mean of its divisors is an integer number (9454548).

Almost surely, 2^51999981 is an apocalyptic number.

It is an amenable number.

51999981 is a deficient number, since it is larger than the sum of its proper divisors (23636403).

51999981 is a wasteful number, since it uses less digits than its factorization.

51999981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1575771.

The product of its digits is 262440, while the sum is 51.

The square root of 51999981 is about 7211.1012335149. The cubic root of 51999981 is about 373.2510702216.

The spelling of 51999981 in words is "fifty-one million, nine hundred ninety-nine thousand, nine hundred eighty-one".