21947780 has 48 divisors (see below), whose sum is σ = 48384000. Its totient is φ = 8351616.

The previous prime is 21947747. The next prime is 21947791. The reversal of 21947780 is 8774912.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45581 + ... + 46059.

It is an arithmetic number, because the mean of its divisors is an integer number (1008000).

Almost surely, 2^21947780 is an apocalyptic number.

21947780 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 21947780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24192000).

21947780 is an abundant number, since it is smaller than the sum of its proper divisors (26436220).

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

21947780 is a wasteful number, since it uses less digits than its factorization.

21947780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 596 (or 594 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 21947780 is about 4684.8457818801. The cubic root of 21947780 is about 279.9820566733.

The spelling of 21947780 in words is "twenty-one million, nine hundred forty-seven thousand, seven hundred eighty".