21851638 has 8 divisors (see below), whose sum is σ = 32921280. Its totient is φ = 10877880.

The previous prime is 21851629. The next prime is 21851657. The reversal of 21851638 is 83615812.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23398 + ... + 24313.

It is an arithmetic number, because the mean of its divisors is an integer number (4115160).

Almost surely, 2^21851638 is an apocalyptic number.

21851638 is a deficient number, since it is larger than the sum of its proper divisors (11069642).

21851638 is a wasteful number, since it uses less digits than its factorization.

21851638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47942.

The product of its digits is 11520, while the sum is 34.

The square root of 21851638 is about 4674.5735634387. The cubic root of 21851638 is about 279.5726388713.

The spelling of 21851638 in words is "twenty-one million, eight hundred fifty-one thousand, six hundred thirty-eight".