21789499 has 2 divisors, whose sum is σ = 21789500. Its totient is φ = 21789498.

The previous prime is 21789473. The next prime is 21789511. The reversal of 21789499 is 99498712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21789499 is a prime.

It is not a weakly prime, because it can be changed into another prime (21789899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10894749 + 10894750.

It is an arithmetic number, because the mean of its divisors is an integer number (10894750).

Almost surely, 2^21789499 is an apocalyptic number.

21789499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21789499 is an equidigital number, since it uses as much as digits as its factorization.

21789499 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 49.

The square root of 21789499 is about 4667.9223429702. The cubic root of 21789499 is about 279.3073825184.

The spelling of 21789499 in words is "twenty-one million, seven hundred eighty-nine thousand, four hundred ninety-nine".