51693981 has 4 divisors (see below), whose sum is σ = 68925312. Its totient is φ = 34462652.

The previous prime is 51693913. The next prime is 51694009. The reversal of 51693981 is 18939615.

51693981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 51693981 - 2¹⁰ = 51692957 is a prime.

It is a super-2 number, since 2×51693981² = 5344535343256722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51695981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8615661 + ... + 8615666.

It is an arithmetic number, because the mean of its divisors is an integer number (17231328).

Almost surely, 2^51693981 is an apocalyptic number.

It is an amenable number.

51693981 is a deficient number, since it is larger than the sum of its proper divisors (17231331).

51693981 is a wasteful number, since it uses less digits than its factorization.

51693981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17231330.

The product of its digits is 58320, while the sum is 42.

The square root of 51693981 is about 7189.8526410491. The cubic root of 51693981 is about 372.5174827763.

The spelling of 51693981 in words is "fifty-one million, six hundred ninety-three thousand, nine hundred eighty-one".