51997781 has 8 divisors (see below), whose sum is σ = 60061824. Its totient is φ = 44489920.

The previous prime is 51997739. The next prime is 51997787. The reversal of 51997781 is 18779915.

51997781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 51997781 - 2²² = 47803477 is a prime.

It is a super-2 number, since 2×51997781² = 5407538457847922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51997787) 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 7 ways as a sum of consecutive naturals, for example, 138845 + ... + 139218.

It is an arithmetic number, because the mean of its divisors is an integer number (7507728).

Almost surely, 2^51997781 is an apocalyptic number.

It is an amenable number.

51997781 is a deficient number, since it is larger than the sum of its proper divisors (8064043).

51997781 is a wasteful number, since it uses less digits than its factorization.

51997781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278091.

The product of its digits is 158760, while the sum is 47.

The square root of 51997781 is about 7210.9486893196. The cubic root of 51997781 is about 373.2458063483.

The spelling of 51997781 in words is "fifty-one million, nine hundred ninety-seven thousand, seven hundred eighty-one".