51515621 has 2 divisors, whose sum is σ = 51515622. Its totient is φ = 51515620.

The previous prime is 51515617. The next prime is 51515623. The reversal of 51515621 is 12651515.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 46430596 + 5085025 = 6814^2 + 2255^2 .

It is a cyclic number.

It is not a de Polignac number, because 51515621 - 2² = 51515617 is a prime.

Together with 51515623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51515623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25757810 + 25757811.

It is an arithmetic number, because the mean of its divisors is an integer number (25757811).

Almost surely, 2^51515621 is an apocalyptic number.

It is an amenable number.

51515621 is a deficient number, since it is larger than the sum of its proper divisors (1).

51515621 is an equidigital number, since it uses as much as digits as its factorization.

51515621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1500, while the sum is 26.

The square root of 51515621 is about 7177.4383313269. The cubic root of 51515621 is about 372.0885561130.

The spelling of 51515621 in words is "fifty-one million, five hundred fifteen thousand, six hundred twenty-one".