21998886 has 64 divisors (see below), whose sum is σ = 55469568. Its totient is φ = 5660928.

The previous prime is 21998863. The next prime is 21998887. The reversal of 21998886 is 68889912.

21998886 = 106² + 107² + ... + 406².

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21998887) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 23010 + ... + 23946.

It is an arithmetic number, because the mean of its divisors is an integer number (866712).

Almost surely, 2^21998886 is an apocalyptic number.

21998886 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21998886, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27734784).

21998886 is an abundant number, since it is smaller than the sum of its proper divisors (33470682).

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

21998886 is a wasteful number, since it uses less digits than its factorization.

21998886 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1005.

The product of its digits is 497664, while the sum is 51.

The square root of 21998886 is about 4690.2970055211. The cubic root of 21998886 is about 280.1992034830.

The spelling of 21998886 in words is "twenty-one million, nine hundred ninety-eight thousand, eight hundred eighty-six".