21309867 has 12 divisors (see below), whose sum is σ = 31842720. Its totient is φ = 13716528.

The previous prime is 21309859. The next prime is 21309877. The reversal of 21309867 is 76890312.

It is not a de Polignac number, because 21309867 - 2³ = 21309859 is a prime.

It is a super-2 number, since 2×21309867² = 908220863115378, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21309877) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 40563 + ... + 41084.

It is an arithmetic number, because the mean of its divisors is an integer number (2653560).

Almost surely, 2^21309867 is an apocalyptic number.

21309867 is a deficient number, since it is larger than the sum of its proper divisors (10532853).

21309867 is a wasteful number, since it uses less digits than its factorization.

21309867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81682 (or 81679 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21309867 is about 4616.2611494585. The cubic root of 21309867 is about 277.2427808887.

The spelling of 21309867 in words is "twenty-one million, three hundred nine thousand, eight hundred sixty-seven".