21057408 has 96 divisors (see below), whose sum is σ = 62931960. Its totient is φ = 7008768.

The previous prime is 21057341. The next prime is 21057419. The reversal of 21057408 is 80475012.

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 (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 30766 + ... + 31442.

Almost surely, 2^21057408 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 21057408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31465980).

21057408 is an abundant number, since it is smaller than the sum of its proper divisors (41874552).

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

21057408 is an frugal number, since it uses more digits than its factorization.

21057408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 706 (or 682 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21057408 is about 4588.8351463089. The cubic root of 21057408 is about 276.1435925779.

The spelling of 21057408 in words is "twenty-one million, fifty-seven thousand, four hundred eight".