51421681 has 4 divisors (see below), whose sum is σ = 51454372. Its totient is φ = 51388992.

The previous prime is 51421649. The next prime is 51421687. The reversal of 51421681 is 18612415.

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 25411681 + 26010000 = 5041^2 + 5100^2 .

It is a cyclic number.

It is not a de Polignac number, because 51421681 - 2⁵ = 51421649 is a prime.

It is a super-2 number, since 2×51421681² = 5288378553731522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51421687) 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, 13860 + ... + 17173.

It is an arithmetic number, because the mean of its divisors is an integer number (12863593).

Almost surely, 2^51421681 is an apocalyptic number.

It is an amenable number.

51421681 is a deficient number, since it is larger than the sum of its proper divisors (32691).

51421681 is a wasteful number, since it uses less digits than its factorization.

51421681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32690.

The product of its digits is 1920, while the sum is 28.

The square root of 51421681 is about 7170.8912277345. The cubic root of 51421681 is about 371.8622476243.

The spelling of 51421681 in words is "fifty-one million, four hundred twenty-one thousand, six hundred eighty-one".