21999281 has 2 divisors, whose sum is σ = 21999282. Its totient is φ = 21999280.

The previous prime is 21999277. The next prime is 21999301. The reversal of 21999281 is 18299912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19439281 + 2560000 = 4409^2 + 1600^2 .

It is a cyclic number.

It is not a de Polignac number, because 21999281 - 2² = 21999277 is a prime.

It is a super-2 number, since 2×21999281² = 967936729033922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21999221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10999640 + 10999641.

It is an arithmetic number, because the mean of its divisors is an integer number (10999641).

Almost surely, 2^21999281 is an apocalyptic number.

It is an amenable number.

21999281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21999281 is an equidigital number, since it uses as much as digits as its factorization.

21999281 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23328, while the sum is 41.

The square root of 21999281 is about 4690.3391135397. The cubic root of 21999281 is about 280.2008805076.

The spelling of 21999281 in words is "twenty-one million, nine hundred ninety-nine thousand, two hundred eighty-one".