21212138 has 8 divisors (see below), whose sum is σ = 31842720. Its totient is φ = 10597900.

The previous prime is 21212131. The next prime is 21212143. The reversal of 21212138 is 83121212.

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

It is not an unprimeable number, because it can be changed into a prime (21212131) 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, 38 + ... + 6513.

It is an arithmetic number, because the mean of its divisors is an integer number (3980340).

Almost surely, 2^21212138 is an apocalyptic number.

21212138 is a deficient number, since it is larger than the sum of its proper divisors (10630582).

21212138 is a wasteful number, since it uses less digits than its factorization.

21212138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8172.

The product of its digits is 192, while the sum is 20.

The square root of 21212138 is about 4605.6636872442. The cubic root of 21212138 is about 276.8183110861.

The spelling of 21212138 in words is "twenty-one million, two hundred twelve thousand, one hundred thirty-eight".