21981143 has 2 divisors, whose sum is σ = 21981144. Its totient is φ = 21981142.

The previous prime is 21981137. The next prime is 21981149. The reversal of 21981143 is 34118912.

It is a balanced prime because it is at equal distance from previous prime (21981137) and next prime (21981149).

It is a cyclic number.

It is not a de Polignac number, because 21981143 - 2⁶ = 21981079 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21981149) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990571 + 10990572.

It is an arithmetic number, because the mean of its divisors is an integer number (10990572).

Almost surely, 2^21981143 is an apocalyptic number.

21981143 is a deficient number, since it is larger than the sum of its proper divisors (1).

21981143 is an equidigital number, since it uses as much as digits as its factorization.

21981143 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1728, while the sum is 29.

The square root of 21981143 is about 4688.4051659386. The cubic root of 21981143 is about 280.1238525211.

The spelling of 21981143 in words is "twenty-one million, nine hundred eighty-one thousand, one hundred forty-three".