21955860 has 60 divisors (see below), whose sum is σ = 68881428. Its totient is φ = 5854464.

The previous prime is 21955859. The next prime is 21955861. The reversal of 21955860 is 6855912.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21955859) and next prime (21955861).

It can be written as a sum of positive squares in 2 ways, for example, as 12702096 + 9253764 = 3564^2 + 3042^2 .

It is a tau number, because it is divible by the number of its divisors (60).

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 (21955861) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 5157 + ... + 8396.

Almost surely, 2^21955860 is an apocalyptic number.

21955860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21955860 is an abundant number, since it is smaller than the sum of its proper divisors (46925568).

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

21955860 is a wasteful number, since it uses less digits than its factorization.

21955860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13574 (or 13563 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 21955860 is about 4685.7080574871. The cubic root of 21955860 is about 280.0164106028.

The spelling of 21955860 in words is "twenty-one million, nine hundred fifty-five thousand, eight hundred sixty".