21891641520 has 160 divisors (see below), whose sum is σ = 79022656512. Its totient is φ = 4909372416.

The previous prime is 21891641479. The next prime is 21891641561. The reversal of 21891641520 is 2514619812.

It is an interprime number because it is at equal distance from previous prime (21891641479) and next prime (21891641561).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 33892 + ... + 211971.

Almost surely, 2^21891641520 is an apocalyptic number.

21891641520 is a gapful number since it is divisible by the number (20) 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 21891641520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39511328256).

21891641520 is an abundant number, since it is smaller than the sum of its proper divisors (57131014992).

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

21891641520 is a wasteful number, since it uses less digits than its factorization.

21891641520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 245939 (or 245933 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 39.

The spelling of 21891641520 in words is "twenty-one billion, eight hundred ninety-one million, six hundred forty-one thousand, five hundred twenty".