21404689 has 2 divisors, whose sum is σ = 21404690. Its totient is φ = 21404688.

The previous prime is 21404681. The next prime is 21404729. The reversal of 21404689 is 98640412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17472400 + 3932289 = 4180^2 + 1983^2 .

It is a cyclic number.

It is not a de Polignac number, because 21404689 - 2³ = 21404681 is a prime.

It is a super-2 number, since 2×21404689² = 916321422373442, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21404681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10702344 + 10702345.

It is an arithmetic number, because the mean of its divisors is an integer number (10702345).

Almost surely, 2^21404689 is an apocalyptic number.

It is an amenable number.

21404689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21404689 is an equidigital number, since it uses as much as digits as its factorization.

21404689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 21404689 is about 4626.5201825994. The cubic root of 21404689 is about 277.6533859695.

The spelling of 21404689 in words is "twenty-one million, four hundred four thousand, six hundred eighty-nine".