51916981 has 4 divisors (see below), whose sum is σ = 52207200. Its totient is φ = 51626764.

The previous prime is 51916973. The next prime is 51917009. The reversal of 51916981 is 18961915.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 51916981 - 2³ = 51916973 is a prime.

It is a super-2 number, since 2×51916981² = 5390745832308722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51916901) 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, 144841 + ... + 145198.

It is an arithmetic number, because the mean of its divisors is an integer number (13051800).

Almost surely, 2^51916981 is an apocalyptic number.

It is an amenable number.

51916981 is a deficient number, since it is larger than the sum of its proper divisors (290219).

51916981 is a wasteful number, since it uses less digits than its factorization.

51916981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290218.

The product of its digits is 19440, while the sum is 40.

The square root of 51916981 is about 7205.3439196197. The cubic root of 51916981 is about 373.0523756854.

The spelling of 51916981 in words is "fifty-one million, nine hundred sixteen thousand, nine hundred eighty-one".