21205754 has 4 divisors (see below), whose sum is σ = 31808634. Its totient is φ = 10602876.

The previous prime is 21205727. The next prime is 21205759. The reversal of 21205754 is 45750212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20457529 + 748225 = 4523^2 + 865^2 .

It is not an unprimeable number, because it can be changed into a prime (21205759) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5301437 + ... + 5301440.

Almost surely, 2^21205754 is an apocalyptic number.

21205754 is a deficient number, since it is larger than the sum of its proper divisors (10602880).

21205754 is a wasteful number, since it uses less digits than its factorization.

21205754 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10602879.

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21205754 is about 4604.9705753674. The cubic root of 21205754 is about 276.7905379087.

Adding to 21205754 its reverse (45750212), we get a palindrome (66955966).

The spelling of 21205754 in words is "twenty-one million, two hundred five thousand, seven hundred fifty-four".