21167989 has 2 divisors, whose sum is σ = 21167990. Its totient is φ = 21167988.

The previous prime is 21167987. The next prime is 21168023. The reversal of 21167989 is 98976112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16402500 + 4765489 = 4050^2 + 2183^2 .

It is a cyclic number.

It is not a de Polignac number, because 21167989 - 2¹ = 21167987 is a prime.

Together with 21167987, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21167987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10583994 + 10583995.

It is an arithmetic number, because the mean of its divisors is an integer number (10583995).

Almost surely, 2^21167989 is an apocalyptic number.

It is an amenable number.

21167989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21167989 is an equidigital number, since it uses as much as digits as its factorization.

21167989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 43.

The square root of 21167989 is about 4600.8682876170. The cubic root of 21167989 is about 276.6261296070.

The spelling of 21167989 in words is "twenty-one million, one hundred sixty-seven thousand, nine hundred eighty-nine".