664021428 has 96 divisors (see below), whose sum is σ = 1882540800. Its totient is φ = 178449408.

The previous prime is 664021403. The next prime is 664021429. The reversal of 664021428 is 824120466.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664021429) 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, 411888 + ... + 413496.

It is an arithmetic number, because the mean of its divisors is an integer number (19609800).

Almost surely, 2^664021428 is an apocalyptic number.

664021428 is a gapful number since it is divisible by the number (68) 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 664021428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (941270400).

664021428 is an abundant number, since it is smaller than the sum of its proper divisors (1218519372).

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

664021428 is a wasteful number, since it uses less digits than its factorization.

664021428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1674 (or 1638 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 33.

The square root of 664021428 is about 25768.6132339325. The cubic root of 664021428 is about 872.4235187734.

The spelling of 664021428 in words is "six hundred sixty-four million, twenty-one thousand, four hundred twenty-eight".