51345721 has 4 divisors (see below), whose sum is σ = 58680832. Its totient is φ = 44010612.

The previous prime is 51345691. The next prime is 51345727. The reversal of 51345721 is 12754315.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-51345721 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 51345721.

It is not an unprimeable number, because it can be changed into a prime (51345727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3667545 + ... + 3667558.

It is an arithmetic number, because the mean of its divisors is an integer number (14670208).

Almost surely, 2^51345721 is an apocalyptic number.

It is an amenable number.

51345721 is a deficient number, since it is larger than the sum of its proper divisors (7335111).

51345721 is an equidigital number, since it uses as much as digits as its factorization.

51345721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7335110.

The product of its digits is 4200, while the sum is 28.

The square root of 51345721 is about 7165.5928575380. The cubic root of 51345721 is about 371.6790526772.

The spelling of 51345721 in words is "fifty-one million, three hundred forty-five thousand, seven hundred twenty-one".