21755646 has 48 divisors (see below), whose sum is σ = 54138240. Its totient is φ = 6244560.

The previous prime is 21755633. The next prime is 21755651. The reversal of 21755646 is 64655712.

It is a happy number.

21755646 is a `hidden beast` number, since 2 + 1 + 7 + 5 + 5 + 646 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21755646.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 871 + ... + 6653.

It is an arithmetic number, because the mean of its divisors is an integer number (1127880).

Almost surely, 2^21755646 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21755646, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27069120).

21755646 is an abundant number, since it is smaller than the sum of its proper divisors (32382594).

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

21755646 is a wasteful number, since it uses less digits than its factorization.

21755646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5821 (or 5818 counting only the distinct ones).

The product of its digits is 50400, while the sum is 36.

The square root of 21755646 is about 4664.2948020038. The cubic root of 21755646 is about 279.1626599955.

The spelling of 21755646 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred forty-six".