21205736 has 32 divisors (see below), whose sum is σ = 42170880. Its totient is φ = 9979200.

The previous prime is 21205727. The next prime is 21205759. The reversal of 21205736 is 63750212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8021 + ... + 10331.

It is an arithmetic number, because the mean of its divisors is an integer number (1317840).

Almost surely, 2^21205736 is an apocalyptic number.

It is an amenable number.

21205736 is a deficient number, since it is larger than the sum of its proper divisors (20965144).

21205736 is a wasteful number, since it uses less digits than its factorization.

21205736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2385 (or 2381 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 26.

The square root of 21205736 is about 4604.9686209572. The cubic root of 21205736 is about 276.7904595930.

Adding to 21205736 its reverse (63750212), we get a palindrome (84955948).

The spelling of 21205736 in words is "twenty-one million, two hundred five thousand, seven hundred thirty-six".