21867321 has 16 divisors (see below), whose sum is σ = 35282304. Its totient is φ = 11760384.

The previous prime is 21867317. The next prime is 21867331. The reversal of 21867321 is 12376812.

It is not a de Polignac number, because 21867321 - 2² = 21867317 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21867331) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30270 + ... + 30983.

It is an arithmetic number, because the mean of its divisors is an integer number (2205144).

Almost surely, 2^21867321 is an apocalyptic number.

21867321 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21867321 is a deficient number, since it is larger than the sum of its proper divisors (13414983).

21867321 is a wasteful number, since it uses less digits than its factorization.

21867321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61280.

The product of its digits is 4032, while the sum is 30.

The square root of 21867321 is about 4676.2507417802. The cubic root of 21867321 is about 279.6395063098.

The spelling of 21867321 in words is "twenty-one million, eight hundred sixty-seven thousand, three hundred twenty-one".