21355638 has 32 divisors (see below), whose sum is σ = 47195136. Its totient is φ = 6407808.

The previous prime is 21355637. The next prime is 21355657. The reversal of 21355638 is 83655312.

It is a junction number, because it is equal to n+sod(n) for n = 21355599 and 21355608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21355637) 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, 2206 + ... + 6897.

It is an arithmetic number, because the mean of its divisors is an integer number (1474848).

Almost surely, 2^21355638 is an apocalyptic number.

21355638 is an abundant number, since it is smaller than the sum of its proper divisors (25839498).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21355638 is a wasteful number, since it uses less digits than its factorization.

21355638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9148.

The product of its digits is 21600, while the sum is 33.

The square root of 21355638 is about 4621.2160737191. The cubic root of 21355638 is about 277.4411335243.

The spelling of 21355638 in words is "twenty-one million, three hundred fifty-five thousand, six hundred thirty-eight".