21871221 has 8 divisors (see below), whose sum is σ = 29220960. Its totient is φ = 14551152.

The previous prime is 21871207. The next prime is 21871237. The reversal of 21871221 is 12217812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21871221 - 2¹⁴ = 21854837 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21871191 and 21871200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21871271) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5635 + ... + 8688.

It is an arithmetic number, because the mean of its divisors is an integer number (3652620).

Almost surely, 2^21871221 is an apocalyptic number.

It is an amenable number.

21871221 is a deficient number, since it is larger than the sum of its proper divisors (7349739).

21871221 is a wasteful number, since it uses less digits than its factorization.

21871221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14835.

The product of its digits is 448, while the sum is 24.

The square root of 21871221 is about 4676.6677239248. The cubic root of 21871221 is about 279.6561297338.

The spelling of 21871221 in words is "twenty-one million, eight hundred seventy-one thousand, two hundred twenty-one".