21612089 has 2 divisors, whose sum is σ = 21612090. Its totient is φ = 21612088.

The previous prime is 21612079. The next prime is 21612091. The reversal of 21612089 is 98021612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 525625 = 4592^2 + 725^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21612089 is a prime.

Together with 21612091, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21612079) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806044 + 10806045.

It is an arithmetic number, because the mean of its divisors is an integer number (10806045).

Almost surely, 2^21612089 is an apocalyptic number.

It is an amenable number.

21612089 is a deficient number, since it is larger than the sum of its proper divisors (1).

21612089 is an equidigital number, since it uses as much as digits as its factorization.

21612089 is an evil number, because the sum of its binary digits is even.

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

The square root of 21612089 is about 4648.8804028497. The cubic root of 21612089 is about 278.5472760376.

The spelling of 21612089 in words is "twenty-one million, six hundred twelve thousand, eighty-nine".