21891996 has 72 divisors (see below), whose sum is σ = 63903840. Its totient is φ = 6189696.

The previous prime is 21891977. The next prime is 21892007. The reversal of 21891996 is 69919812.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27070 + ... + 27866.

Almost surely, 2^21891996 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21891996, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31951920).

21891996 is an abundant number, since it is smaller than the sum of its proper divisors (42011844).

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

21891996 is a wasteful number, since it uses less digits than its factorization.

21891996 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 923 (or 918 counting only the distinct ones).

The product of its digits is 69984, while the sum is 45.

The square root of 21891996 is about 4678.8883295073. Note that the first 3 decimals coincide. The cubic root of 21891996 is about 279.7446481497.

The spelling of 21891996 in words is "twenty-one million, eight hundred ninety-one thousand, nine hundred ninety-six".