21591999253890 has 512 divisors, whose sum is σ = 68415798528000. Its totient is φ = 4794509131776.

The previous prime is 21591999253849. The next prime is 21591999253901. The reversal of 21591999253890 is 9835299919512.

21591999253890 is a `hidden beast` number, since 2 + 1 + 59 + 199 + 9 + 2 + 5 + 389 + 0 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 237023371 + ... + 237114449.

It is an arithmetic number, because the mean of its divisors is an integer number (133624606500).

Almost surely, 2^{21591999253890} is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21591999253890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34207899264000).

21591999253890 is an abundant number, since it is smaller than the sum of its proper divisors (46823799274110).

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

21591999253890 is a wasteful number, since it uses less digits than its factorization.

21591999253890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91291 (or 91285 counting only the distinct ones).

The product of its (nonzero) digits is 141717600, while the sum is 72.

The spelling of 21591999253890 in words is "twenty-one trillion, five hundred ninety-one billion, nine hundred ninety-nine million, two hundred fifty-three thousand, eight hundred ninety".