21390826 has 4 divisors (see below), whose sum is σ = 32086242. Its totient is φ = 10695412.

The previous prime is 21390797. The next prime is 21390833. The reversal of 21390826 is 62809312.

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., 14447601 + 6943225 = 3801^2 + 2635^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

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, 5347705 + ... + 5347708.

Almost surely, 2^21390826 is an apocalyptic number.

21390826 is a deficient number, since it is larger than the sum of its proper divisors (10695416).

21390826 is a wasteful number, since it uses less digits than its factorization.

21390826 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10695415.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 21390826 is about 4625.0217296787. The cubic root of 21390826 is about 277.5934311911.

The spelling of 21390826 in words is "twenty-one million, three hundred ninety thousand, eight hundred twenty-six".