13215661 has 2 divisors, whose sum is σ = 13215662. Its totient is φ = 13215660.

The previous prime is 13215617. The next prime is 13215691. The reversal of 13215661 is 16651231.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9954025 + 3261636 = 3155^2 + 1806^2 .

It is a cyclic number.

It is not a de Polignac number, because 13215661 - 2⁷ = 13215533 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13215691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6607830 + 6607831.

It is an arithmetic number, because the mean of its divisors is an integer number (6607831).

Almost surely, 2^13215661 is an apocalyptic number.

It is an amenable number.

13215661 is a deficient number, since it is larger than the sum of its proper divisors (1).

13215661 is an equidigital number, since it uses as much as digits as its factorization.

13215661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1080, while the sum is 25.

The square root of 13215661 is about 3635.3350602111. The cubic root of 13215661 is about 236.4265781408.

Adding to 13215661 its reverse (16651231), we get a palindrome (29866892).

The spelling of 13215661 in words is "thirteen million, two hundred fifteen thousand, six hundred sixty-one".