51291038721 has 8 divisors (see below), whose sum is σ = 73648671040. Its totient is φ = 31563716112.

The previous prime is 51291038717. The next prime is 51291038753. The reversal of 51291038721 is 12783019215.

It is a happy number.

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

It is not a de Polignac number, because 51291038721 - 2² = 51291038717 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 1315154839 = 51291038721 / (5 + 1 + 2 + 9 + 1 + 0 + 3 + 8 + 7 + 2 + 1).

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 51291038721.

It is not an unprimeable number, because it can be changed into a prime (51291038221) 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, 657577381 + ... + 657577458.

It is an arithmetic number, because the mean of its divisors is an integer number (9206083880).

Almost surely, 2^51291038721 is an apocalyptic number.

It is an amenable number.

51291038721 is a deficient number, since it is larger than the sum of its proper divisors (22357632319).

51291038721 is a wasteful number, since it uses less digits than its factorization.

51291038721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1315154855.

The product of its (nonzero) digits is 30240, while the sum is 39.

The spelling of 51291038721 in words is "fifty-one billion, two hundred ninety-one million, thirty-eight thousand, seven hundred twenty-one".