51215665 has 12 divisors (see below), whose sum is σ = 62807796. Its totient is φ = 40092128.

The previous prime is 51215663. The next prime is 51215677. The reversal of 51215665 is 56651215.

It can be written as a sum of positive squares in 2 ways, for example, as 15586704 + 35628961 = 3948^2 + 5969^2 .

It is not a de Polignac number, because 51215665 - 2¹ = 51215663 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 (51215663) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8727 + ... + 13363.

It is an arithmetic number, because the mean of its divisors is an integer number (5233983).

Almost surely, 2^51215665 is an apocalyptic number.

It is an amenable number.

51215665 is a deficient number, since it is larger than the sum of its proper divisors (11592131).

51215665 is an equidigital number, since it uses as much as digits as its factorization.

51215665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4736 (or 4689 counting only the distinct ones).

The product of its digits is 9000, while the sum is 31.

The square root of 51215665 is about 7156.5120694372. The cubic root of 51215665 is about 371.3649728739.

The spelling of 51215665 in words is "fifty-one million, two hundred fifteen thousand, six hundred sixty-five".