51997681 has 8 divisors (see below), whose sum is σ = 53578664. Its totient is φ = 50440320.

The previous prime is 51997669. The next prime is 51997697. The reversal of 51997681 is 18679915.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 5198400 + 46799281 = 2280^2 + 6841^2 .

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 51997681 - 2¹⁹ = 51473393 is a prime.

It is a super-2 number, since 2×51997681² = 5407517658755522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51997601) 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, 1386 + ... + 10291.

It is an arithmetic number, because the mean of its divisors is an integer number (6697333).

Almost surely, 2^51997681 is an apocalyptic number.

It is an amenable number.

51997681 is a deficient number, since it is larger than the sum of its proper divisors (1580983).

51997681 is a wasteful number, since it uses less digits than its factorization.

51997681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11811.

The product of its digits is 136080, while the sum is 46.

The square root of 51997681 is about 7210.9417554159. The cubic root of 51997681 is about 373.2455670778.

It can be divided in two parts, 5199 and 7681, that added together give a triangular number (12880 = T₁₆₀).

The spelling of 51997681 in words is "fifty-one million, nine hundred ninety-seven thousand, six hundred eighty-one".