21988434 has 64 divisors (see below), whose sum is σ = 51327360. Its totient is φ = 6220800.

The previous prime is 21988411. The next prime is 21988451. The reversal of 21988434 is 43488912.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a junction number, because it is equal to n+sod(n) for n = 21988392 and 21988401.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 54634 + ... + 55034.

It is an arithmetic number, because the mean of its divisors is an integer number (801990).

Almost surely, 2^21988434 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21988434, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25663680).

21988434 is an abundant number, since it is smaller than the sum of its proper divisors (29338926).

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

21988434 is a wasteful number, since it uses less digits than its factorization.

21988434 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475.

The product of its digits is 55296, while the sum is 39.

The square root of 21988434 is about 4689.1826579906. The cubic root of 21988434 is about 280.1548208415.

It can be divided in two parts, 21988 and 434, that added together give a palindrome (22422).

The spelling of 21988434 in words is "twenty-one million, nine hundred eighty-eight thousand, four hundred thirty-four".