21000026 has 4 divisors (see below), whose sum is σ = 31500042. Its totient is φ = 10500012.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000026 is 62000012.

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., 20839225 + 160801 = 4565^2 + 401^2 .

It is a junction number, because it is equal to n+sod(n) for n = 20999980 and 21000016.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250005 + ... + 5250008.

Almost surely, 2^21000026 is an apocalyptic number.

21000026 is a deficient number, since it is larger than the sum of its proper divisors (10500016).

21000026 is a wasteful number, since it uses less digits than its factorization.

21000026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10500015.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21000026 is about 4582.5785317875. The cubic root of 21000026 is about 275.8925314984.

Adding to 21000026 its reverse (62000012), we get a palindrome (83000038).

The spelling of 21000026 in words is "twenty-one million, twenty-six", and thus it is an aban number and an uban number.