51708721 has 8 divisors (see below), whose sum is σ = 54008640. Its totient is φ = 49456368.

The previous prime is 51708707. The next prime is 51708731. The reversal of 51708721 is 12780715.

It is a happy number.

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 51708721 - 2⁵ = 51708689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (51708731) 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, 9661 + ... + 14026.

It is an arithmetic number, because the mean of its divisors is an integer number (6751080).

Almost surely, 2^51708721 is an apocalyptic number.

It is an amenable number.

51708721 is a deficient number, since it is larger than the sum of its proper divisors (2299919).

51708721 is a wasteful number, since it uses less digits than its factorization.

51708721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23783.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 51708721 is about 7190.8776237675. The cubic root of 51708721 is about 372.5528859043.

The spelling of 51708721 in words is "fifty-one million, seven hundred eight thousand, seven hundred twenty-one".