21065707 has 4 divisors (see below), whose sum is σ = 22686160. Its totient is φ = 19445256.

The previous prime is 21065701. The next prime is 21065711. The reversal of 21065707 is 70756012.

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 21065707 - 2¹⁵ = 21032939 is a prime.

It is a super-2 number, since 2×21065707² = 887528022819698, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21065701) 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, 810207 + ... + 810232.

It is an arithmetic number, because the mean of its divisors is an integer number (5671540).

Almost surely, 2^21065707 is an apocalyptic number.

21065707 is a deficient number, since it is larger than the sum of its proper divisors (1620453).

21065707 is a wasteful number, since it uses less digits than its factorization.

21065707 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1620452.

The product of its (nonzero) digits is 2940, while the sum is 28.

The square root of 21065707 is about 4589.7393172162. The cubic root of 21065707 is about 276.1798650808.

The spelling of 21065707 in words is "twenty-one million, sixty-five thousand, seven hundred seven".