21605298 has 64 divisors (see below), whose sum is σ = 51408000. Its totient is φ = 6002880.

The previous prime is 21605293. The next prime is 21605321. The reversal of 21605298 is 89250612.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21605293) 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 31 ways as a sum of consecutive naturals, for example, 144928 + ... + 145076.

It is an arithmetic number, because the mean of its divisors is an integer number (803250).

Almost surely, 2^21605298 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21605298, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25704000).

21605298 is an abundant number, since it is smaller than the sum of its proper divisors (29802702).

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

21605298 is a wasteful number, since it uses less digits than its factorization.

21605298 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204 (or 178 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 33.

The square root of 21605298 is about 4648.1499545518. The cubic root of 21605298 is about 278.5180977273.

The spelling of 21605298 in words is "twenty-one million, six hundred five thousand, two hundred ninety-eight".