21129867 has 18 divisors (see below), whose sum is σ = 33549516. Its totient is φ = 12805320.

The previous prime is 21129863. The next prime is 21129869. The reversal of 21129867 is 76892112.

It is not a de Polignac number, because 21129867 - 2² = 21129863 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21129863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 8613 + ... + 10790.

It is an arithmetic number, because the mean of its divisors is an integer number (1863862).

Almost surely, 2^21129867 is an apocalyptic number.

21129867 is a deficient number, since it is larger than the sum of its proper divisors (12419649).

21129867 is a wasteful number, since it uses less digits than its factorization.

21129867 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19431 (or 19417 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21129867 is about 4596.7235070211. The cubic root of 21129867 is about 276.4599686767.

The spelling of 21129867 in words is "twenty-one million, one hundred twenty-nine thousand, eight hundred sixty-seven".