1515665561 has 2 divisors, whose sum is σ = 1515665562. Its totient is φ = 1515665560.

The previous prime is 1515665533. The next prime is 1515665579. The reversal of 1515665561 is 1655665151.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1343662336 + 172003225 = 36656^2 + 13115^2 .

It is a cyclic number.

It is not a de Polignac number, because 1515665561 - 2¹⁰ = 1515664537 is a prime.

It is not a weakly prime, because it can be changed into another prime (1515665861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 757832780 + 757832781.

It is an arithmetic number, because the mean of its divisors is an integer number (757832781).

Almost surely, 2^1515665561 is an apocalyptic number.

It is an amenable number.

1515665561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1515665561 is an equidigital number, since it uses as much as digits as its factorization.

1515665561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 135000, while the sum is 41.

The square root of 1515665561 is about 38931.5496865974. The cubic root of 1515665561 is about 1148.6854698697.

The spelling of 1515665561 in words is "one billion, five hundred fifteen million, six hundred sixty-five thousand, five hundred sixty-one".