21661992 has 96 divisors (see below), whose sum is σ = 66437280. Its totient is φ = 6557760.

The previous prime is 21661973. The next prime is 21661993. The reversal of 21661992 is 29916612.

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

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21661993) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20878 + ... + 21890.

It is an arithmetic number, because the mean of its divisors is an integer number (692055).

Almost surely, 2^21661992 is an apocalyptic number.

21661992 is a gapful number since it is divisible by the number (22) 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 21661992, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33218640).

21661992 is an abundant number, since it is smaller than the sum of its proper divisors (44775288).

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

21661992 is a wasteful number, since it uses less digits than its factorization.

21661992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1045 (or 1029 counting only the distinct ones).

The product of its digits is 11664, while the sum is 36.

The square root of 21661992 is about 4654.2445144191. The cubic root of 21661992 is about 278.7615027394.

The spelling of 21661992 in words is "twenty-one million, six hundred sixty-one thousand, nine hundred ninety-two".