21429684 has 42 divisors (see below), whose sum is σ = 56234850. Its totient is φ = 7142256.

The previous prime is 21429671. The next prime is 21429691. The reversal of 21429684 is 48692412.

It can be written as a sum of positive squares in only one way, i.e., 19607184 + 1822500 = 4428^2 + 1350^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 759 + ... + 6590.

It is an arithmetic number, because the mean of its divisors is an integer number (1338925).

Almost surely, 2^21429684 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 21429684, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28117425).

21429684 is an abundant number, since it is smaller than the sum of its proper divisors (34805166).

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

21429684 is an equidigital number, since it uses as much as digits as its factorization.

21429684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7371 (or 7354 counting only the distinct ones).

The product of its digits is 27648, while the sum is 36.

The square root of 21429684 is about 4629.2206687519. The cubic root of 21429684 is about 277.7614191018.

The spelling of 21429684 in words is "twenty-one million, four hundred twenty-nine thousand, six hundred eighty-four".