21221516 has 12 divisors (see below), whose sum is σ = 37555560. Its totient is φ = 10491360.

The previous prime is 21221509. The next prime is 21221521. The reversal of 21221516 is 61512212.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29450 + ... + 30161.

It is an arithmetic number, because the mean of its divisors is an integer number (3129630).

Almost surely, 2^21221516 is an apocalyptic number.

It is an amenable number.

21221516 is a deficient number, since it is larger than the sum of its proper divisors (16334044).

21221516 is a wasteful number, since it uses less digits than its factorization.

21221516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59704 (or 59702 counting only the distinct ones).

The product of its digits is 240, while the sum is 20.

The square root of 21221516 is about 4606.6816690542. The cubic root of 21221516 is about 276.8590993625.

Adding to 21221516 its reverse (61512212), we get a palindrome (82733728).

The spelling of 21221516 in words is "twenty-one million, two hundred twenty-one thousand, five hundred sixteen".