51515551621 has 2 divisors, whose sum is σ = 51515551622. Its totient is φ = 51515551620.

The previous prime is 51515551613. The next prime is 51515551643. The reversal of 51515551621 is 12615551515.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 34110026721 + 17405524900 = 184689^2 + 131930^2 .

It is a cyclic number.

It is not a de Polignac number, because 51515551621 - 2³ = 51515551613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51515551421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25757775810 + 25757775811.

It is an arithmetic number, because the mean of its divisors is an integer number (25757775811).

Almost surely, 2^51515551621 is an apocalyptic number.

It is an amenable number.

51515551621 is a deficient number, since it is larger than the sum of its proper divisors (1).

51515551621 is an equidigital number, since it uses as much as digits as its factorization.

51515551621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37500, while the sum is 37.

The spelling of 51515551621 in words is "fifty-one billion, five hundred fifteen million, five hundred fifty-one thousand, six hundred twenty-one".