21278013 has 16 divisors (see below), whose sum is σ = 29877120. Its totient is φ = 13443584.

The previous prime is 21277987. The next prime is 21278021. The reversal of 21278013 is 31087212.

It is a cyclic number.

It is not a de Polignac number, because 21278013 - 2²² = 17083709 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21278063) 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 15 ways as a sum of consecutive naturals, for example, 6433 + ... + 9161.

It is an arithmetic number, because the mean of its divisors is an integer number (1867320).

Almost surely, 2^21278013 is an apocalyptic number.

21278013 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21278013 is a deficient number, since it is larger than the sum of its proper divisors (8599107).

21278013 is a wasteful number, since it uses less digits than its factorization.

21278013 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2868.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21278013 is about 4612.8096644019. The cubic root of 21278013 is about 277.1045711173.

The spelling of 21278013 in words is "twenty-one million, two hundred seventy-eight thousand, thirteen".