21078394 has 8 divisors (see below), whose sum is σ = 31638708. Its totient is φ = 10532160.

The previous prime is 21078371. The next prime is 21078403. The reversal of 21078394 is 49387012.

It can be written as a sum of positive squares in 2 ways, for example, as 21022225 + 56169 = 4585^2 + 237^2 .

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

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 3 ways as a sum of consecutive naturals, for example, 1884 + ... + 6760.

Almost surely, 2^21078394 is an apocalyptic number.

21078394 is a deficient number, since it is larger than the sum of its proper divisors (10560314).

21078394 is a wasteful number, since it uses less digits than its factorization.

21078394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7040.

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21078394 is about 4591.1212138213. The cubic root of 21078394 is about 276.2352978396.

It can be divided in two parts, 2107 and 8394, that added together give a palindrome (10501).

The spelling of 21078394 in words is "twenty-one million, seventy-eight thousand, three hundred ninety-four".