51681605 has 4 divisors (see below), whose sum is σ = 62017932. Its totient is φ = 41345280.

The previous prime is 51681601. The next prime is 51681611. The reversal of 51681605 is 50618615.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8213956 + 43467649 = 2866^2 + 6593^2 .

It is not a de Polignac number, because 51681605 - 2² = 51681601 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51681601) 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, 5168156 + ... + 5168165.

It is an arithmetic number, because the mean of its divisors is an integer number (15504483).

Almost surely, 2^51681605 is an apocalyptic number.

It is an amenable number.

51681605 is a deficient number, since it is larger than the sum of its proper divisors (10336327).

51681605 is a wasteful number, since it uses less digits than its factorization.

51681605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10336326.

The product of its (nonzero) digits is 7200, while the sum is 32.

The square root of 51681605 is about 7188.9919321140. The cubic root of 51681605 is about 372.4877524012.

The spelling of 51681605 in words is "fifty-one million, six hundred eighty-one thousand, six hundred five".