21012573 has 4 divisors (see below), whose sum is σ = 28016768. Its totient is φ = 14008380.

The previous prime is 21012569. The next prime is 21012581. The reversal of 21012573 is 37521012.

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 not a de Polignac number, because 21012573 - 2² = 21012569 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 (21012503) 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, 3502093 + ... + 3502098.

It is an arithmetic number, because the mean of its divisors is an integer number (7004192).

Almost surely, 2^21012573 is an apocalyptic number.

It is an amenable number.

21012573 is a deficient number, since it is larger than the sum of its proper divisors (7004195).

21012573 is an equidigital number, since it uses as much as digits as its factorization.

21012573 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7004194.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21012573 is about 4583.9473164512. The cubic root of 21012573 is about 275.9474668972.

Adding to 21012573 its reverse (37521012), we get a palindrome (58533585).

The spelling of 21012573 in words is "twenty-one million, twelve thousand, five hundred seventy-three".