21000946 has 4 divisors (see below), whose sum is σ = 31501422. Its totient is φ = 10500472.

The previous prime is 21000913. The next prime is 21000953. The reversal of 21000946 is 64900012.

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., 16900321 + 4100625 = 4111^2 + 2025^2 .

It is a Smith number, since the sum of its digits (22) 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 (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250235 + ... + 5250238.

Almost surely, 2^21000946 is an apocalyptic number.

21000946 is a deficient number, since it is larger than the sum of its proper divisors (10500476).

21000946 is a wasteful number, since it uses less digits than its factorization.

21000946 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10500475.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21000946 is about 4582.6789108555. The cubic root of 21000946 is about 275.8965603414.

Adding to 21000946 its reverse (64900012), we get a palindrome (85900958).

The spelling of 21000946 in words is "twenty-one million, nine hundred forty-six", and thus it is an aban number.