21221646 has 32 divisors (see below), whose sum is σ = 44040480. Its totient is φ = 6811776.

The previous prime is 21221633. The next prime is 21221653. The reversal of 21221646 is 64612212.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 23760 + ... + 24636.

It is an arithmetic number, because the mean of its divisors is an integer number (1376265).

Almost surely, 2^21221646 is an apocalyptic number.

21221646 is an abundant number, since it is smaller than the sum of its proper divisors (22818834).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21221646 is a wasteful number, since it uses less digits than its factorization.

21221646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1028.

The product of its digits is 1152, while the sum is 24.

The square root of 21221646 is about 4606.6957789722. The cubic root of 21221646 is about 276.8596646946.

Adding to 21221646 its reverse (64612212), we get a palindrome (85833858).

The spelling of 21221646 in words is "twenty-one million, two hundred twenty-one thousand, six hundred forty-six".