21611898 has 96 divisors (see below), whose sum is σ = 60383232. Its totient is φ = 5421600.

The previous prime is 21611897. The next prime is 21611917. The reversal of 21611898 is 89811612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21611893) 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 47 ways as a sum of consecutive naturals, for example, 42715 + ... + 43217.

It is an arithmetic number, because the mean of its divisors is an integer number (628992).

Almost surely, 2^21611898 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21611898, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30191616).

21611898 is an abundant number, since it is smaller than the sum of its proper divisors (38771334).

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

21611898 is a wasteful number, since it uses less digits than its factorization.

21611898 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 560 (or 557 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 21611898 is about 4648.8598602238. The cubic root of 21611898 is about 278.5464554677.

The spelling of 21611898 in words is "twenty-one million, six hundred eleven thousand, eight hundred ninety-eight".