21205499 has 8 divisors (see below), whose sum is σ = 24576768. Its totient is φ = 17919720.

The previous prime is 21205453. The next prime is 21205523. The reversal of 21205499 is 99450212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21205499 - 2⁸ = 21205243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21205099) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20837 + ... + 21830.

It is an arithmetic number, because the mean of its divisors is an integer number (3072096).

Almost surely, 2^21205499 is an apocalyptic number.

21205499 is a deficient number, since it is larger than the sum of its proper divisors (3371269).

21205499 is an equidigital number, since it uses as much as digits as its factorization.

21205499 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42745.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 21205499 is about 4604.9428878109. The cubic root of 21205499 is about 276.7894284320.

The spelling of 21205499 in words is "twenty-one million, two hundred five thousand, four hundred ninety-nine".