15878643661 has 2 divisors, whose sum is σ = 15878643662. Its totient is φ = 15878643660.

The previous prime is 15878643611. The next prime is 15878643679. The reversal of 15878643661 is 16634687851.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9306460900 + 6572182761 = 96470^2 + 81069^2 .

It is a cyclic number.

It is not a de Polignac number, because 15878643661 - 2¹¹ = 15878641613 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15878643611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7939321830 + 7939321831.

It is an arithmetic number, because the mean of its divisors is an integer number (7939321831).

Almost surely, 2^15878643661 is an apocalyptic number.

It is an amenable number.

15878643661 is a deficient number, since it is larger than the sum of its proper divisors (1).

15878643661 is an equidigital number, since it uses as much as digits as its factorization.

15878643661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5806080, while the sum is 55.

The spelling of 15878643661 in words is "fifteen billion, eight hundred seventy-eight million, six hundred forty-three thousand, six hundred sixty-one".