21012065 has 4 divisors (see below), whose sum is σ = 25214484. Its totient is φ = 16809648.

The previous prime is 21012059. The next prime is 21012073. The reversal of 21012065 is 56021012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2211169 + 18800896 = 1487^2 + 4336^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012065 - 2¹⁶ = 20946529 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2101202 + ... + 2101211.

It is an arithmetic number, because the mean of its divisors is an integer number (6303621).

Almost surely, 2^21012065 is an apocalyptic number.

It is an amenable number.

21012065 is a deficient number, since it is larger than the sum of its proper divisors (4202419).

21012065 is an equidigital number, since it uses as much as digits as its factorization.

21012065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4202418.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21012065 is about 4583.8919053573. The cubic root of 21012065 is about 275.9452431105.

Adding to 21012065 its reverse (56021012), we get a palindrome (77033077).

The spelling of 21012065 in words is "twenty-one million, twelve thousand, sixty-five".