21667616 has 12 divisors (see below), whose sum is σ = 42658182. Its totient is φ = 10833792.

The previous prime is 21667603. The next prime is 21667649. The reversal of 21667616 is 61676612.

It can be written as a sum of positive squares in only one way, i.e., 16810000 + 4857616 = 4100^2 + 2204^2 .

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

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 as a sum of consecutive naturals, namely, 338525 + ... + 338588.

Almost surely, 2^21667616 is an apocalyptic number.

It is an amenable number.

21667616 is a deficient number, since it is larger than the sum of its proper divisors (20990566).

21667616 is an equidigital number, since it uses as much as digits as its factorization.

21667616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 677123 (or 677115 counting only the distinct ones).

The product of its digits is 18144, while the sum is 35.

The square root of 21667616 is about 4654.8486548974. The cubic root of 21667616 is about 278.7856251598.

The spelling of 21667616 in words is "twenty-one million, six hundred sixty-seven thousand, six hundred sixteen".