16821997440 has 64 divisors (see below), whose sum is σ = 53620122960. Its totient is φ = 4485865472.

The previous prime is 16821997417. The next prime is 16821997457. The reversal of 16821997440 is 4479912861.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4378809 + ... + 4382648.

Almost surely, 2^16821997440 is an apocalyptic number.

16821997440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

16821997440 is an abundant number, since it is smaller than the sum of its proper divisors (36798125520).

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

16821997440 is an equidigital number, since it uses as much as digits as its factorization.

16821997440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8761479 (or 8761467 counting only the distinct ones).

The product of its (nonzero) digits is 870912, while the sum is 51.

The spelling of 16821997440 in words is "sixteen billion, eight hundred twenty-one million, nine hundred ninety-seven thousand, four hundred forty".