21945689 has 2 divisors, whose sum is σ = 21945690. Its totient is φ = 21945688.

The previous prime is 21945673. The next prime is 21945751. The reversal of 21945689 is 98654912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21576025 + 369664 = 4645^2 + 608^2 .

It is a cyclic number.

It is not a de Polignac number, because 21945689 - 2⁴ = 21945673 is a prime.

It is a super-2 number, since 2×21945689² = 963226531369442, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21945659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10972844 + 10972845.

It is an arithmetic number, because the mean of its divisors is an integer number (10972845).

Almost surely, 2^21945689 is an apocalyptic number.

It is an amenable number.

21945689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21945689 is an equidigital number, since it uses as much as digits as its factorization.

21945689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 155520, while the sum is 44.

The square root of 21945689 is about 4684.6226102003. The cubic root of 21945689 is about 279.9731649452.

The spelling of 21945689 in words is "twenty-one million, nine hundred forty-five thousand, six hundred eighty-nine".