21997986140 has 96 divisors (see below), whose sum is σ = 51992672256. Its totient is φ = 7757164800.

The previous prime is 21997986121. The next prime is 21997986149. The reversal of 21997986140 is 4168979912.

It is a super-2 number, since 2×21997986140² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21997986149) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4440665 + ... + 4445615.

It is an arithmetic number, because the mean of its divisors is an integer number (541590336).

Almost surely, 2^21997986140 is an apocalyptic number.

21997986140 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 21997986140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25996336128).

21997986140 is an abundant number, since it is smaller than the sum of its proper divisors (29994686116).

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

21997986140 is a wasteful number, since it uses less digits than its factorization.

21997986140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5739 (or 5737 counting only the distinct ones).

The product of its (nonzero) digits is 1959552, while the sum is 56.

The spelling of 21997986140 in words is "twenty-one billion, nine hundred ninety-seven million, nine hundred eighty-six thousand, one hundred forty".