21218930 has 8 divisors (see below), whose sum is σ = 38194092. Its totient is φ = 8487568.

The previous prime is 21218929. The next prime is 21218933. The reversal of 21218930 is 3981212.

It can be written as a sum of positive squares in 2 ways, for example, as 21169201 + 49729 = 4601^2 + 223^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21218930.

It is not an unprimeable number, because it can be changed into a prime (21218933) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1060937 + ... + 1060956.

Almost surely, 2^21218930 is an apocalyptic number.

21218930 is a deficient number, since it is larger than the sum of its proper divisors (16975162).

21218930 is a wasteful number, since it uses less digits than its factorization.

21218930 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2121900.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21218930 is about 4606.4009812434. The cubic root of 21218930 is about 276.8478531237.

The spelling of 21218930 in words is "twenty-one million, two hundred eighteen thousand, nine hundred thirty".