21026791 has 4 divisors (see below), whose sum is σ = 21050784. Its totient is φ = 21002800.

The previous prime is 21026779. The next prime is 21026801. The reversal of 21026791 is 19762012.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21026791 - 2¹¹ = 21024743 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21026741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10630 + ... + 12451.

It is an arithmetic number, because the mean of its divisors is an integer number (5262696).

Almost surely, 2^21026791 is an apocalyptic number.

21026791 is a deficient number, since it is larger than the sum of its proper divisors (23993).

21026791 is an equidigital number, since it uses as much as digits as its factorization.

21026791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23992.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21026791 is about 4585.4979009918. The cubic root of 21026791 is about 276.0096921262.

The spelling of 21026791 in words is "twenty-one million, twenty-six thousand, seven hundred ninety-one".