21394778 has 8 divisors (see below), whose sum is σ = 32207220. Its totient is φ = 10659040.

The previous prime is 21394777. The next prime is 21394781. The reversal of 21394778 is 87749312.

It can be written as a sum of positive squares in 2 ways, for example, as 20857489 + 537289 = 4567^2 + 733^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21394771) 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 3 ways as a sum of consecutive naturals, for example, 18473 + ... + 19596.

Almost surely, 2^21394778 is an apocalyptic number.

21394778 is a deficient number, since it is larger than the sum of its proper divisors (10812442).

21394778 is a wasteful number, since it uses less digits than its factorization.

21394778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 38352.

The product of its digits is 84672, while the sum is 41.

The square root of 21394778 is about 4625.4489511830. The cubic root of 21394778 is about 277.6105254614.

The spelling of 21394778 in words is "twenty-one million, three hundred ninety-four thousand, seven hundred seventy-eight".