21191940 has 216 divisors, whose sum is σ = 81332160. Its totient is φ = 4371840.

The previous prime is 21191923. The next prime is 21191959. The reversal of 21191940 is 4919112.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 152391 + ... + 152529.

Almost surely, 2^21191940 is an apocalyptic number.

21191940 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 21191940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40666080).

21191940 is an abundant number, since it is smaller than the sum of its proper divisors (60140220).

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

21191940 is a wasteful number, since it uses less digits than its factorization.

21191940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183 (or 167 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 21191940 is about 4603.4704300126. The cubic root of 21191940 is about 276.7304219129.

The spelling of 21191940 in words is "twenty-one million, one hundred ninety-one thousand, nine hundred forty".