21378212 has 6 divisors (see below), whose sum is σ = 37411878. Its totient is φ = 10689104.

The previous prime is 21378209. The next prime is 21378223. The reversal of 21378212 is 21287312.

It can be written as a sum of positive squares in only one way, i.e., 21307456 + 70756 = 4616^2 + 266^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2672273 + ... + 2672280.

It is an arithmetic number, because the mean of its divisors is an integer number (6235313).

Almost surely, 2^21378212 is an apocalyptic number.

It is an amenable number.

21378212 is a deficient number, since it is larger than the sum of its proper divisors (16033666).

21378212 is a wasteful number, since it uses less digits than its factorization.

21378212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5344557 (or 5344555 counting only the distinct ones).

The product of its digits is 1344, while the sum is 26.

The square root of 21378212 is about 4623.6578593144. The cubic root of 21378212 is about 277.5388555824.

The spelling of 21378212 in words is "twenty-one million, three hundred seventy-eight thousand, two hundred twelve".