21689959 has 2 divisors, whose sum is σ = 21689960. Its totient is φ = 21689958.

The previous prime is 21689947. The next prime is 21689971. The reversal of 21689959 is 95998612.

It is a balanced prime because it is at equal distance from previous prime (21689947) and next prime (21689971).

It is a cyclic number.

It is not a de Polignac number, because 21689959 - 2¹⁹ = 21165671 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21689159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10844979 + 10844980.

It is an arithmetic number, because the mean of its divisors is an integer number (10844980).

Almost surely, 2^21689959 is an apocalyptic number.

21689959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21689959 is an equidigital number, since it uses as much as digits as its factorization.

21689959 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 349920, while the sum is 49.

The square root of 21689959 is about 4657.2480071390. The cubic root of 21689959 is about 278.8814173846.

The spelling of 21689959 in words is "twenty-one million, six hundred eighty-nine thousand, nine hundred fifty-nine".