21858221 has 8 divisors (see below), whose sum is σ = 27251904. Its totient is φ = 17032320.

The previous prime is 21858217. The next prime is 21858259. The reversal of 21858221 is 12285812.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21858221 - 2² = 21858217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21854221) 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, 141860 + ... + 142013.

It is an arithmetic number, because the mean of its divisors is an integer number (3406488).

Almost surely, 2^21858221 is an apocalyptic number.

It is an amenable number.

21858221 is a deficient number, since it is larger than the sum of its proper divisors (5393683).

21858221 is a wasteful number, since it uses less digits than its factorization.

21858221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 283891.

The product of its digits is 2560, while the sum is 29.

The square root of 21858221 is about 4675.2776388146. The cubic root of 21858221 is about 279.6007106326.

The spelling of 21858221 in words is "twenty-one million, eight hundred fifty-eight thousand, two hundred twenty-one".