21253766 has 4 divisors (see below), whose sum is σ = 31880652. Its totient is φ = 10626882.

The previous prime is 21253763. The next prime is 21253849. The reversal of 21253766 is 66735212.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21253763) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5313440 + ... + 5313443.

It is an arithmetic number, because the mean of its divisors is an integer number (7970163).

Almost surely, 2^21253766 is an apocalyptic number.

21253766 is a deficient number, since it is larger than the sum of its proper divisors (10626886).

21253766 is a wasteful number, since it uses less digits than its factorization.

21253766 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10626885.

The product of its digits is 15120, while the sum is 32.

The square root of 21253766 is about 4610.1806906021. The cubic root of 21253766 is about 276.9992745010. Note that the first 3 decimals are identical.

Adding to 21253766 its reverse (66735212), we get a palindrome (87988978).

The spelling of 21253766 in words is "twenty-one million, two hundred fifty-three thousand, seven hundred sixty-six".