21096981 has 12 divisors (see below), whose sum is σ = 30776460. Its totient is φ = 13924800.

The previous prime is 21096979. The next prime is 21096991. The reversal of 21096981 is 18969012.

It can be written as a sum of positive squares in 2 ways, for example, as 18404100 + 2692881 = 4290^2 + 1641^2 .

It is not a de Polignac number, because 21096981 - 2¹ = 21096979 is a prime.

It is a super-2 number, since 2×21096981² = 890165214628722, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21096931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10696 + ... + 12513.

It is an arithmetic number, because the mean of its divisors is an integer number (2564705).

Almost surely, 2^21096981 is an apocalyptic number.

It is an amenable number.

21096981 is a deficient number, since it is larger than the sum of its proper divisors (9679479).

21096981 is a wasteful number, since it uses less digits than its factorization.

21096981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23316 (or 23313 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21096981 is about 4593.1450009770. The cubic root of 21096981 is about 276.3164690624.

The spelling of 21096981 in words is "twenty-one million, ninety-six thousand, nine hundred eighty-one".