21785689 has 2 divisors, whose sum is σ = 21785690. Its totient is φ = 21785688.

The previous prime is 21785681. The next prime is 21785713. The reversal of 21785689 is 98658712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16646400 + 5139289 = 4080^2 + 2267^2 .

It is a cyclic number.

It is not a de Polignac number, because 21785689 - 2³ = 21785681 is a prime.

It is a super-3 number, since 3×21785689³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21785681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10892844 + 10892845.

It is an arithmetic number, because the mean of its divisors is an integer number (10892845).

Almost surely, 2^21785689 is an apocalyptic number.

It is an amenable number.

21785689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21785689 is an equidigital number, since it uses as much as digits as its factorization.

21785689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 241920, while the sum is 46.

The square root of 21785689 is about 4667.5142206532. The cubic root of 21785689 is about 279.2911021508.

The spelling of 21785689 in words is "twenty-one million, seven hundred eighty-five thousand, six hundred eighty-nine".