20991213900000 has 864 divisors, whose sum is σ = 76808274955776. Its totient is φ = 5435337600000.

The previous prime is 20991213899993. The next prime is 20991213900037. The reversal of 20991213900000 is 931219902.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 4281297549 + ... + 4281302451.

It is an arithmetic number, because the mean of its divisors is an integer number (88898466384).

Almost surely, 2^{20991213900000} is an apocalyptic number.

20991213900000 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 20991213900000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38404137477888).

20991213900000 is an abundant number, since it is smaller than the sum of its proper divisors (55817061055776).

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

20991213900000 is an equidigital number, since it uses as much as digits as its factorization.

20991213900000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5082 (or 5051 counting only the distinct ones).

The product of its (nonzero) digits is 8748, while the sum is 36.

The spelling of 20991213900000 in words is "twenty trillion, nine hundred ninety-one billion, two hundred thirteen million, nine hundred thousand".