21558891840 has 112 divisors (see below), whose sum is σ = 68564101632. Its totient is φ = 5739411456.

The previous prime is 21558891839. The next prime is 21558891841. The reversal of 21558891840 is 4819885512.

It is an interprime number because it is at equal distance from previous prime (21558891839) and next prime (21558891841).

It is a zygodrome in base 4.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21558891841) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 564222 + ... + 601218.

Almost surely, 2^21558891840 is an apocalyptic number.

21558891840 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 21558891840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34282050816).

21558891840 is an abundant number, since it is smaller than the sum of its proper divisors (47005209792).

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

21558891840 is a wasteful number, since it uses less digits than its factorization.

21558891840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37624 (or 37614 counting only the distinct ones).

The product of its (nonzero) digits is 921600, while the sum is 51.

The spelling of 21558891840 in words is "twenty-one billion, five hundred fifty-eight million, eight hundred ninety-one thousand, eight hundred forty".