21010099981 has 8 divisors (see below), whose sum is σ = 22640685984. Its totient is φ = 19381574640.

The previous prime is 21010099967. The next prime is 21010099987. The reversal of 21010099981 is 18999001012.

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

It is a cyclic number.

It is not a de Polignac number, because 21010099981 - 2⁵ = 21010099949 is a prime.

It is a super-2 number, since 2×21010099981² (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 (21010099987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 493951 + ... + 534796.

It is an arithmetic number, because the mean of its divisors is an integer number (2830085748).

Almost surely, 2^21010099981 is an apocalyptic number.

It is an amenable number.

21010099981 is a deficient number, since it is larger than the sum of its proper divisors (1630586003).

21010099981 is a wasteful number, since it uses less digits than its factorization.

21010099981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1030331.

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

The spelling of 21010099981 in words is "twenty-one billion, ten million, ninety-nine thousand, nine hundred eighty-one".