21001000099981 has 16 divisors (see below), whose sum is σ = 23025883392000. Its totient is φ = 18995405180400.

The previous prime is 21001000099949. The next prime is 21001000100057. The reversal of 21001000099981 is 18999000010012.

It is not a de Polignac number, because 21001000099981 - 2⁵ = 21001000099949 is a prime.

It is a super-2 number, since 2×21001000099981² (a number of 27 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 (21001000099181) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 111192216 + ... + 111380926.

It is an arithmetic number, because the mean of its divisors is an integer number (1439117712000).

Almost surely, 2^{21001000099981} is an apocalyptic number.

It is an amenable number.

21001000099981 is a deficient number, since it is larger than the sum of its proper divisors (2024883292019).

21001000099981 is a wasteful number, since it uses less digits than its factorization.

21001000099981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 239760.

The product of its (nonzero) digits is 11664, while the sum is 40.

The spelling of 21001000099981 in words is "twenty-one trillion, one billion, ninety-nine thousand, nine hundred eighty-one".