21081617181 has 24 divisors (see below), whose sum is σ = 32799372320. Its totient is φ = 13005056736.

The previous prime is 21081617171. The next prime is 21081617197. The reversal of 21081617181 is 18171618012.

21081617181 is a `hidden beast` number, since 21 + 0 + 8 + 1 + 617 + 18 + 1 = 666.

It is not a de Polignac number, because 21081617181 - 2⁵ = 21081617149 is a prime.

It is a super-2 number, since 2×21081617181² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081617101) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1426186 + ... + 1440891.

Almost surely, 2^21081617181 is an apocalyptic number.

It is an amenable number.

21081617181 is a deficient number, since it is larger than the sum of its proper divisors (11717755139).

21081617181 is a wasteful number, since it uses less digits than its factorization.

21081617181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2867145 (or 2867142 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 36.

The spelling of 21081617181 in words is "twenty-one billion, eighty-one million, six hundred seventeen thousand, one hundred eighty-one".