20981211 has 4 divisors (see below), whose sum is σ = 27974952. Its totient is φ = 13987472.

The previous prime is 20981201. The next prime is 20981231. The reversal of 20981211 is 11218902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20981211 - 2⁹ = 20980699 is a prime.

It is a super-2 number, since 2×20981211² = 880422430053042, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20981201) 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 3 ways as a sum of consecutive naturals, for example, 3496866 + ... + 3496871.

It is an arithmetic number, because the mean of its divisors is an integer number (6993738).

Almost surely, 2^20981211 is an apocalyptic number.

20981211 is a deficient number, since it is larger than the sum of its proper divisors (6993741).

20981211 is an equidigital number, since it uses as much as digits as its factorization.

20981211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6993740.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 20981211 is about 4580.5251882290. The cubic root of 20981211 is about 275.8101114573.

The spelling of 20981211 in words is "twenty million, nine hundred eighty-one thousand, two hundred eleven".