21221518 has 32 divisors (see below), whose sum is σ = 35108640. Its totient is φ = 9584640.

The previous prime is 21221509. The next prime is 21221521. The reversal of 21221518 is 81512212.

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, 82446 + ... + 82702.

It is an arithmetic number, because the mean of its divisors is an integer number (1097145).

Almost surely, 2^21221518 is an apocalyptic number.

21221518 is a deficient number, since it is larger than the sum of its proper divisors (13887122).

21221518 is a wasteful number, since it uses less digits than its factorization.

21221518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 372.

The product of its digits is 320, while the sum is 22.

The square root of 21221518 is about 4606.6818861302. The cubic root of 21221518 is about 276.8591080600.

The spelling of 21221518 in words is "twenty-one million, two hundred twenty-one thousand, five hundred eighteen".