21378026 has 4 divisors (see below), whose sum is σ = 32067042. Its totient is φ = 10689012.

The previous prime is 21378023. The next prime is 21378041. The reversal of 21378026 is 62087312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20566225 + 811801 = 4535^2 + 901^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21378026.

It is not an unprimeable number, because it can be changed into a prime (21378023) 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 as a sum of consecutive naturals, namely, 5344505 + ... + 5344508.

Almost surely, 2^21378026 is an apocalyptic number.

21378026 is a deficient number, since it is larger than the sum of its proper divisors (10689016).

21378026 is a wasteful number, since it uses less digits than its factorization.

21378026 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10689015.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21378026 is about 4623.6377453256. The cubic root of 21378026 is about 277.5380506760.

The spelling of 21378026 in words is "twenty-one million, three hundred seventy-eight thousand, twenty-six".