21945000 has 320 divisors, whose sum is σ = 89971200. Its totient is φ = 4320000.

The previous prime is 21944987. The next prime is 21945017. The reversal of 21945000 is 54912.

21945000 = T₄₅₅ + T₄₅₆ + ... + T₆₀₈.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

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 79 ways as a sum of consecutive naturals, for example, 1154991 + ... + 1155009.

It is an arithmetic number, because the mean of its divisors is an integer number (281160).

Almost surely, 2^21945000 is an apocalyptic number.

21945000 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 21945000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44985600).

21945000 is an abundant number, since it is smaller than the sum of its proper divisors (68026200).

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

21945000 is a wasteful number, since it uses less digits than its factorization.

21945000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66 (or 47 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 21945000 is about 4684.5490711487. The cubic root of 21945000 is about 279.9702349312.

Adding to 21945000 its reverse (54912), we get a palindrome (21999912).

The spelling of 21945000 in words is "twenty-one million, nine hundred forty-five thousand".