21217898 has 16 divisors (see below), whose sum is σ = 34511400. Its totient is φ = 9725376.

The previous prime is 21217849. The next prime is 21217907. The reversal of 21217898 is 89871212.

It can be written as a sum of positive squares in 4 ways, for example, as 17581249 + 3636649 = 4193^2 + 1907^2 .

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 7 ways as a sum of consecutive naturals, for example, 1136 + ... + 6612.

Almost surely, 2^21217898 is an apocalyptic number.

21217898 is a deficient number, since it is larger than the sum of its proper divisors (13293502).

21217898 is a wasteful number, since it uses less digits than its factorization.

21217898 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5641.

The product of its digits is 16128, while the sum is 38.

The square root of 21217898 is about 4606.2889618434. The cubic root of 21217898 is about 276.8433648104.

The spelling of 21217898 in words is "twenty-one million, two hundred seventeen thousand, eight hundred ninety-eight".