16661581581 has 8 divisors (see below), whose sum is σ = 22216446304. Its totient is φ = 11107218960.

The previous prime is 16661581579. The next prime is 16661581583. The reversal of 16661581581 is 18518516661.

It is an interprime number because it is at equal distance from previous prime (16661581579) and next prime (16661581583).

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

It is not a de Polignac number, because 16661581581 - 2¹ = 16661581579 is a prime.

It is a super-2 number, since 2×16661581581² (a number of 21 digits) contains 22 as substring.

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 16661581581.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16661581583) 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, 39715 + ... + 186816.

It is an arithmetic number, because the mean of its divisors is an integer number (2777055788).

Almost surely, 2^16661581581 is an apocalyptic number.

It is an amenable number.

16661581581 is a deficient number, since it is larger than the sum of its proper divisors (5554864723).

16661581581 is a wasteful number, since it uses less digits than its factorization.

16661581581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251051.

The product of its digits is 345600, while the sum is 48.

The spelling of 16661581581 in words is "sixteen billion, six hundred sixty-one million, five hundred eighty-one thousand, five hundred eighty-one".