21939660 has 120 divisors (see below), whose sum is σ = 71351280. Its totient is φ = 5636736.

The previous prime is 21939653. The next prime is 21939667. The reversal of 21939660 is 6693912.

It is an interprime number because it is at equal distance from previous prime (21939653) and next prime (21939667).

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

It is not an unprimeable number, because it can be changed into a prime (21939667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 46747 + ... + 47213.

It is an arithmetic number, because the mean of its divisors is an integer number (594594).

Almost surely, 2^21939660 is an apocalyptic number.

21939660 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 21939660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35675640).

21939660 is an abundant number, since it is smaller than the sum of its proper divisors (49411620).

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

21939660 is a wasteful number, since it uses less digits than its factorization.

21939660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 517 (or 506 counting only the distinct ones).

The product of its (nonzero) digits is 17496, while the sum is 36.

The square root of 21939660 is about 4683.9790776646. The cubic root of 21939660 is about 279.9475241795.

The spelling of 21939660 in words is "twenty-one million, nine hundred thirty-nine thousand, six hundred sixty".