21243378 has 16 divisors (see below), whose sum is σ = 45755136. Its totient is φ = 6536400.

The previous prime is 21243361. The next prime is 21243403. The reversal of 21243378 is 87334212.

It is a super-3 number, since 3×21243378³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 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, 136098 + ... + 136253.

It is an arithmetic number, because the mean of its divisors is an integer number (2859696).

Almost surely, 2^21243378 is an apocalyptic number.

21243378 is an abundant number, since it is smaller than the sum of its proper divisors (24511758).

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

21243378 is a wasteful number, since it uses less digits than its factorization.

21243378 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 272369.

The product of its digits is 8064, while the sum is 30.

The square root of 21243378 is about 4609.0539159355. The cubic root of 21243378 is about 276.9541383843.

The spelling of 21243378 in words is "twenty-one million, two hundred forty-three thousand, three hundred seventy-eight".