1515201661 has 2 divisors, whose sum is σ = 1515201662. Its totient is φ = 1515201660.

The previous prime is 1515201587. The next prime is 1515201673. The reversal of 1515201661 is 1661025151.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1324596025 + 190605636 = 36395^2 + 13806^2 .

It is an emirp because it is prime and its reverse (1661025151) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1515201661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1515201691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 757600830 + 757600831.

It is an arithmetic number, because the mean of its divisors is an integer number (757600831).

Almost surely, 2^1515201661 is an apocalyptic number.

It is an amenable number.

1515201661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1515201661 is an equidigital number, since it uses as much as digits as its factorization.

1515201661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1800, while the sum is 28.

The square root of 1515201661 is about 38925.5913378333. The cubic root of 1515201661 is about 1148.5682651296.

It can be divided in two parts, 151520 and 1661, that added together give a triangular number (153181 = T₅₅₃).

The spelling of 1515201661 in words is "one billion, five hundred fifteen million, two hundred one thousand, six hundred sixty-one".