21981960 has 384 divisors, whose sum is σ = 97493760. Its totient is φ = 4147200.

The previous prime is 21981941. The next prime is 21981961. The reversal of 21981960 is 6918912.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981961) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 360330 + ... + 360390.

It is an arithmetic number, because the mean of its divisors is an integer number (253890).

Almost surely, 2^21981960 is an apocalyptic number.

21981960 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 21981960, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (48746880).

21981960 is an abundant number, since it is smaller than the sum of its proper divisors (75511800).

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

21981960 is a wasteful number, since it uses less digits than its factorization.

21981960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109 (or 102 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21981960 is about 4688.4922949707. The cubic root of 21981960 is about 280.1273230466.

The spelling of 21981960 in words is "twenty-one million, nine hundred eighty-one thousand, nine hundred sixty".