21755636 has 12 divisors (see below), whose sum is σ = 43511328.
Its totient is φ = 9323832.
The previous prime is 21755633. The next prime is 21755651. The reversal of 21755636 is 63655712.
21755636 is an admirable number.
It is a junction number, because it is equal to n+sod(n) for n = 21755596 and 21755605.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (21755633) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 388466 + ... + 388521.
It is an arithmetic number, because the mean of its divisors is an integer number (3625944).
Almost surely, 221755636 is an apocalyptic number.
It is an amenable number.
21755636 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
21755636 is a wasteful number, since it uses less digits than its factorization.
21755636 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 776998 (or 776996 counting only the distinct ones).
The product of its digits is 37800, while the sum is 35.
The square root of 21755636 is about 4664.2937300303.
The cubic root of 21755636 is about 279.1626172230.
The spelling of 21755636 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred thirty-six".