21891660448 has 24 divisors (see below), whose sum is σ = 49256236512. Its totient is φ = 9382140096.

The previous prime is 21891660443. The next prime is 21891660449. The reversal of 21891660448 is 84406619812.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21891660443) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 48865090 + ... + 48865537.

It is an arithmetic number, because the mean of its divisors is an integer number (2052343188).

Almost surely, 2^21891660448 is an apocalyptic number.

21891660448 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21891660448 is an abundant number, since it is smaller than the sum of its proper divisors (27364576064).

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

21891660448 is an equidigital number, since it uses as much as digits as its factorization.

21891660448 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97730644 (or 97730636 counting only the distinct ones).

The product of its (nonzero) digits is 663552, while the sum is 49.

The spelling of 21891660448 in words is "twenty-one billion, eight hundred ninety-one million, six hundred sixty thousand, four hundred forty-eight".