21104981 has 2 divisors, whose sum is σ = 21104982. Its totient is φ = 21104980.

The previous prime is 21104947. The next prime is 21104989. The reversal of 21104981 is 18940112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20566225 + 538756 = 4535^2 + 734^2 .

It is a cyclic number.

It is not a de Polignac number, because 21104981 - 2¹⁸ = 20842837 is a prime.

It is a super-4 number, since 4×21104981⁴ (a number of 30 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21104981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21104989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552490 + 10552491.

It is an arithmetic number, because the mean of its divisors is an integer number (10552491).

Almost surely, 2^21104981 is an apocalyptic number.

It is an amenable number.

21104981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21104981 is an equidigital number, since it uses as much as digits as its factorization.

21104981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 21104981 is about 4594.0157814270. The cubic root of 21104981 is about 276.3513911586.

The spelling of 21104981 in words is "twenty-one million, one hundred four thousand, nine hundred eighty-one".