16821840 has 320 divisors, whose sum is σ = 68567040. Its totient is φ = 3317760.

The previous prime is 16821839. The next prime is 16821869. The reversal of 16821840 is 4812861.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 16821798 and 16821807.

It is a congruent number.

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, 542625 + ... + 542655.

It is an arithmetic number, because the mean of its divisors is an integer number (214272).

Almost surely, 2^16821840 is an apocalyptic number.

16821840 is a gapful number since it is divisible by the number (10) 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 16821840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34283520).

16821840 is an abundant number, since it is smaller than the sum of its proper divisors (51745200).

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

16821840 is a wasteful number, since it uses less digits than its factorization.

16821840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90 (or 84 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 16821840 is about 4101.4436482780. The cubic root of 16821840 is about 256.2267684670.

The spelling of 16821840 in words is "sixteen million, eight hundred twenty-one thousand, eight hundred forty".