21020867 has 4 divisors (see below), whose sum is σ = 24023856. Its totient is φ = 18017880.

The previous prime is 21020863. The next prime is 21020893. The reversal of 21020867 is 76802012.

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 21020867 - 2² = 21020863 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21020863) 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, 1501484 + ... + 1501497.

It is an arithmetic number, because the mean of its divisors is an integer number (6005964).

Almost surely, 2^21020867 is an apocalyptic number.

21020867 is a deficient number, since it is larger than the sum of its proper divisors (3002989).

21020867 is an equidigital number, since it uses as much as digits as its factorization.

21020867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3002988.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21020867 is about 4584.8519060053. The cubic root of 21020867 is about 275.9837690868.

Adding to 21020867 its reverse (76802012), we get a palindrome (97822879).

The spelling of 21020867 in words is "twenty-one million, twenty thousand, eight hundred sixty-seven".