21035981 has 2 divisors, whose sum is σ = 21035982. Its totient is φ = 21035980.

The previous prime is 21035929. The next prime is 21036013. The reversal of 21035981 is 18953012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19061956 + 1974025 = 4366^2 + 1405^2 .

It is a cyclic number.

It is not a de Polignac number, because 21035981 - 2¹⁴ = 21019597 is a prime.

It is a super-2 number, since 2×21035981² = 885024993264722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21035921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10517990 + 10517991.

It is an arithmetic number, because the mean of its divisors is an integer number (10517991).

Almost surely, 2^21035981 is an apocalyptic number.

It is an amenable number.

21035981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21035981 is an equidigital number, since it uses as much as digits as its factorization.

21035981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 21035981 is about 4586.4998637305. The cubic root of 21035981 is about 276.0498973359.

Adding to 21035981 its reverse (18953012), we get a palindrome (39988993).

The spelling of 21035981 in words is "twenty-one million, thirty-five thousand, nine hundred eighty-one".