21178212 has 24 divisors (see below), whose sum is σ = 53908512. Its totient is φ = 6417600.

The previous prime is 21178211. The next prime is 21178219. The reversal of 21178212 is 21287112.

It is not an unprimeable number, because it can be changed into a prime (21178211) by changing a digit.

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, 80089 + ... + 80352.

It is an arithmetic number, because the mean of its divisors is an integer number (2246188).

Almost surely, 2^21178212 is an apocalyptic number.

21178212 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21178212 is an abundant number, since it is smaller than the sum of its proper divisors (32730300).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21178212 is a wasteful number, since it uses less digits than its factorization.

21178212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160459 (or 160457 counting only the distinct ones).

The product of its digits is 448, while the sum is 24.

The square root of 21178212 is about 4601.9791394573. The cubic root of 21178212 is about 276.6706542868.

Subtracting 21178212 from its reverse (21287112), we obtain a square (108900 = 330²).

The spelling of 21178212 in words is "twenty-one million, one hundred seventy-eight thousand, two hundred twelve".