15661665807 has 4 divisors (see below), whose sum is σ = 20882221080. Its totient is φ = 10441110536.

The previous prime is 15661665787. The next prime is 15661665889. The reversal of 15661665807 is 70856616651.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 15661665807 - 2¹⁶ = 15661600271 is a prime.

It is a super-2 number, since 2×15661665807² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 15661665807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15661665907) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2610277632 + ... + 2610277637.

It is an arithmetic number, because the mean of its divisors is an integer number (5220555270).

Almost surely, 2^15661665807 is an apocalyptic number.

15661665807 is a deficient number, since it is larger than the sum of its proper divisors (5220555273).

15661665807 is an equidigital number, since it uses as much as digits as its factorization.

15661665807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5220555272.

The product of its (nonzero) digits is 1814400, while the sum is 51.

The spelling of 15661665807 in words is "fifteen billion, six hundred sixty-one million, six hundred sixty-five thousand, eight hundred seven".