21394728 has 48 divisors (see below), whose sum is σ = 58331520. Its totient is φ = 7083936.

The previous prime is 21394697. The next prime is 21394733. The reversal of 21394728 is 82749312.

It is a Smith number, since the sum of its digits (36) 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 (36).

It is a junction number, because it is equal to n+sod(n) for n = 21394692 and 21394701.

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 11 ways as a sum of consecutive naturals, for example, 10825 + ... + 12647.

It is an arithmetic number, because the mean of its divisors is an integer number (1215240).

Almost surely, 2^21394728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21394728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29165760).

21394728 is an abundant number, since it is smaller than the sum of its proper divisors (36936792).

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

21394728 is a wasteful number, since it uses less digits than its factorization.

21394728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1998 (or 1991 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 21394728 is about 4625.4435462991. The cubic root of 21394728 is about 277.6103092009.

It can be divided in two parts, 21394 and 728, that added together give a palindrome (22122).

The spelling of 21394728 in words is "twenty-one million, three hundred ninety-four thousand, seven hundred twenty-eight".