21015073 has 4 divisors (see below), whose sum is σ = 21027888. Its totient is φ = 21002260.

The previous prime is 21015067. The next prime is 21015079. The reversal of 21015073 is 37051012.

It is the 1872-nd star number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (21015067) and next prime (21015079).

It is a cyclic number.

It is not a de Polignac number, because 21015073 - 2⁵ = 21015041 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21015073.

It is not an unprimeable number, because it can be changed into a prime (21015079) 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, 3511 + ... + 7372.

It is an arithmetic number, because the mean of its divisors is an integer number (5256972).

Almost surely, 2^21015073 is an apocalyptic number.

It is an amenable number.

21015073 is a deficient number, since it is larger than the sum of its proper divisors (12815).

21015073 is a wasteful number, since it uses less digits than its factorization.

21015073 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12814.

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21015073 is about 4584.2199990838. The cubic root of 21015073 is about 275.9584102074.

Adding to 21015073 its reverse (37051012), we get a palindrome (58066085).

The spelling of 21015073 in words is "twenty-one million, fifteen thousand, seventy-three".