215581517661 has 8 divisors (see below), whose sum is σ = 287485753984. Its totient is φ = 143699146560.

The previous prime is 215581517639. The next prime is 215581517783. The reversal of 215581517661 is 166715185512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 215581517661 - 2¹⁸ = 215581255517 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 215581517661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215581517161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5443285 + ... + 5482746.

It is an arithmetic number, because the mean of its divisors is an integer number (35935719248).

Almost surely, 2^215581517661 is an apocalyptic number.

It is an amenable number.

215581517661 is a deficient number, since it is larger than the sum of its proper divisors (71904236323).

215581517661 is a wasteful number, since it uses less digits than its factorization.

215581517661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10932611.

The product of its digits is 504000, while the sum is 48.

The spelling of 215581517661 in words is "two hundred fifteen billion, five hundred eighty-one million, five hundred seventeen thousand, six hundred sixty-one".