21917040 has 160 divisors (see below), whose sum is σ = 72852480. Its totient is φ = 5440512.

The previous prime is 21917023. The next prime is 21917113. The reversal of 21917040 is 4071912.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21917040.

It is a congruent number.

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 31 ways as a sum of consecutive naturals, for example, 327087 + ... + 327153.

It is an arithmetic number, because the mean of its divisors is an integer number (455328).

Almost surely, 2^21917040 is an apocalyptic number.

21917040 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 21917040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36426240).

21917040 is an abundant number, since it is smaller than the sum of its proper divisors (50935440).

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

21917040 is a wasteful number, since it uses less digits than its factorization.

21917040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159 (or 153 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21917040 is about 4681.5638412821. The cubic root of 21917040 is about 279.8512815683.

Adding to 21917040 its reverse (4071912), we get a palindrome (25988952).

The spelling of 21917040 in words is "twenty-one million, nine hundred seventeen thousand, forty".