21321278 has 16 divisors (see below), whose sum is σ = 34960896. Its totient is φ = 9671640.

The previous prime is 21321277. The next prime is 21321283. The reversal of 21321278 is 87212312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21321277) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18425 + ... + 19547.

It is an arithmetic number, because the mean of its divisors is an integer number (2185056).

Almost surely, 2^21321278 is an apocalyptic number.

21321278 is a deficient number, since it is larger than the sum of its proper divisors (13639618).

21321278 is a wasteful number, since it uses less digits than its factorization.

21321278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1999.

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

The square root of 21321278 is about 4617.4969409844. The cubic root of 21321278 is about 277.2922580136.

The spelling of 21321278 in words is "twenty-one million, three hundred twenty-one thousand, two hundred seventy-eight".