21005099181 has 36 divisors (see below), whose sum is σ = 33847567936. Its totient is φ = 12540314160.

The previous prime is 21005099177. The next prime is 21005099201. The reversal of 21005099181 is 18199050012.

It is not a de Polignac number, because 21005099181 - 2² = 21005099177 is a prime.

It is a super-2 number, since 2×21005099181² (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 (21005099281) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 70981 + ... + 216906.

Almost surely, 2^21005099181 is an apocalyptic number.

It is an amenable number.

21005099181 is a deficient number, since it is larger than the sum of its proper divisors (12842468755).

21005099181 is a wasteful number, since it uses less digits than its factorization.

21005099181 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287982 (or 287968 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 36.

The spelling of 21005099181 in words is "twenty-one billion, five million, ninety-nine thousand, one hundred eighty-one".