21640189 has 2 divisors, whose sum is σ = 21640190. Its totient is φ = 21640188.

The previous prime is 21640187. The next prime is 21640219. The reversal of 21640189 is 98104612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21622500 + 17689 = 4650^2 + 133^2 .

It is a cyclic number.

It is not a de Polignac number, because 21640189 - 2¹ = 21640187 is a prime.

Together with 21640187, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21640189.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21640181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10820094 + 10820095.

It is an arithmetic number, because the mean of its divisors is an integer number (10820095).

Almost surely, 2^21640189 is an apocalyptic number.

It is an amenable number.

21640189 is a deficient number, since it is larger than the sum of its proper divisors (1).

21640189 is an equidigital number, since it uses as much as digits as its factorization.

21640189 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21640189 is about 4651.9016541625. The cubic root of 21640189 is about 278.6679459801.

The spelling of 21640189 in words is "twenty-one million, six hundred forty thousand, one hundred eighty-nine".