66921888 has 96 divisors (see below), whose sum is σ = 193536000. Its totient is φ = 20079360.

The previous prime is 66921887. The next prime is 66921917. The reversal of 66921888 is 88812966.

It is a tau number, because it is divible by the number of its divisors (96).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is not an unprimeable number, because it can be changed into a prime (66921887) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 133863 + ... + 134361.

It is an arithmetic number, because the mean of its divisors is an integer number (2016000).

Almost surely, 2^66921888 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 66921888, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96768000).

66921888 is an abundant number, since it is smaller than the sum of its proper divisors (126614112).

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

66921888 is a wasteful number, since it uses less digits than its factorization.

66921888 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 650 (or 642 counting only the distinct ones).

The product of its digits is 331776, while the sum is 48.

The square root of 66921888 is about 8180.5799305428. The cubic root of 66921888 is about 405.9969100366.

The spelling of 66921888 in words is "sixty-six million, nine hundred twenty-one thousand, eight hundred eighty-eight".