21858621 has 8 divisors (see below), whose sum is σ = 29259264. Its totient is φ = 14515200.

The previous prime is 21858581. The next prime is 21858623. The reversal of 21858621 is 12685812.

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

It is not a de Polignac number, because 21858621 - 2¹³ = 21850429 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21858623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13405 + ... + 14946.

It is an arithmetic number, because the mean of its divisors is an integer number (3657408).

Almost surely, 2^21858621 is an apocalyptic number.

It is an amenable number.

21858621 is a deficient number, since it is larger than the sum of its proper divisors (7400643).

21858621 is a wasteful number, since it uses less digits than its factorization.

21858621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28611.

The product of its digits is 7680, while the sum is 33.

The square root of 21858621 is about 4675.3204168271. The cubic root of 21858621 is about 279.6024161633.

The spelling of 21858621 in words is "twenty-one million, eight hundred fifty-eight thousand, six hundred twenty-one".