21064428 has 192 divisors, whose sum is σ = 72576000. Its totient is φ = 5114880.

The previous prime is 21064363. The next prime is 21064471. The reversal of 21064428 is 82446012.

21064428 is a `hidden beast` number, since 2 + 10 + 644 + 2 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 141298 + ... + 141446.

It is an arithmetic number, because the mean of its divisors is an integer number (378000).

Almost surely, 2^21064428 is an apocalyptic number.

21064428 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21064428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36288000).

21064428 is an abundant number, since it is smaller than the sum of its proper divisors (51511572).

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

21064428 is a wasteful number, since it uses less digits than its factorization.

21064428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197 (or 189 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 21064428 is about 4589.5999825693. The cubic root of 21064428 is about 276.1742755667.

The spelling of 21064428 in words is "twenty-one million, sixty-four thousand, four hundred twenty-eight".