21100981 has 8 divisors (see below), whose sum is σ = 23101344. Its totient is φ = 19114320.

The previous prime is 21100969. The next prime is 21100993. The reversal of 21100981 is 18900112.

It is an interprime number because it is at equal distance from previous prime (21100969) and next prime (21100993).

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 21100981 - 2⁵ = 21100949 is a prime.

It is a super-2 number, since 2×21100981² = 890502798324722, which 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 (21100901) 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, 51 + ... + 6496.

It is an arithmetic number, because the mean of its divisors is an integer number (2887668).

Almost surely, 2^21100981 is an apocalyptic number.

It is an amenable number.

21100981 is a deficient number, since it is larger than the sum of its proper divisors (2000363).

21100981 is a wasteful number, since it uses less digits than its factorization.

21100981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6851.

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 21100981 is about 4593.5804118356. The cubic root of 21100981 is about 276.3339312138. Note that the first 3 decimals are identical.

The spelling of 21100981 in words is "twenty-one million, one hundred thousand, nine hundred eighty-one".