21645750 has 192 divisors, whose sum is σ = 68290560. Its totient is φ = 4536000.

The previous prime is 21645749. The next prime is 21645751. The reversal of 21645750 is 5754612.

It is an interprime number because it is at equal distance from previous prime (21645749) and next prime (21645751).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a plaindrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21645751) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 698235 + ... + 698265.

It is an arithmetic number, because the mean of its divisors is an integer number (355680).

Almost surely, 2^21645750 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21645750, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34145280).

21645750 is an abundant number, since it is smaller than the sum of its proper divisors (46644810).

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

21645750 is a wasteful number, since it uses less digits than its factorization.

21645750 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84 (or 67 counting only the distinct ones).

The product of its (nonzero) digits is 8400, while the sum is 30.

The square root of 21645750 is about 4652.4993283181. The cubic root of 21645750 is about 278.6918142208.

The spelling of 21645750 in words is "twenty-one million, six hundred forty-five thousand, seven hundred fifty".