21521366 has 8 divisors (see below), whose sum is σ = 32341680. Its totient is φ = 10740808.

The previous prime is 21521341. The next prime is 21521369. The reversal of 21521366 is 66312512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521369) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8546 + ... + 10773.

It is an arithmetic number, because the mean of its divisors is an integer number (4042710).

Almost surely, 2^21521366 is an apocalyptic number.

21521366 is a deficient number, since it is larger than the sum of its proper divisors (10820314).

21521366 is a wasteful number, since it uses less digits than its factorization.

21521366 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19878.

The product of its digits is 2160, while the sum is 26.

The square root of 21521366 is about 4639.1126306655. The cubic root of 21521366 is about 278.1569684416.

Adding to 21521366 its reverse (66312512), we get a palindrome (87833878).

The spelling of 21521366 in words is "twenty-one million, five hundred twenty-one thousand, three hundred sixty-six".