21205790 has 8 divisors (see below), whose sum is σ = 38170440. Its totient is φ = 8482312.

The previous prime is 21205781. The next prime is 21205801. The reversal of 21205790 is 9750212.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1060280 + ... + 1060299.

It is an arithmetic number, because the mean of its divisors is an integer number (4771305).

Almost surely, 2^21205790 is an apocalyptic number.

21205790 is a deficient number, since it is larger than the sum of its proper divisors (16964650).

21205790 is a wasteful number, since it uses less digits than its factorization.

21205790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2120586.

The product of its (nonzero) digits is 1260, while the sum is 26.

The square root of 21205790 is about 4604.9744841856. The cubic root of 21205790 is about 276.7906945400.

The spelling of 21205790 in words is "twenty-one million, two hundred five thousand, seven hundred ninety".