21999240 has 96 divisors (see below), whose sum is σ = 72909720. Its totient is φ = 5750784.

The previous prime is 21999221. The next prime is 21999269. The reversal of 21999240 is 4299912.

21999240 = T₃₃₉ + T₃₄₀ + ... + T₅₅₄.

It can be written as a sum of positive squares in 4 ways, for example, as 21178404 + 820836 = 4602^2 + 906^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21999195 and 21999204.

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 23 ways as a sum of consecutive naturals, for example, 18504 + ... + 19656.

Almost surely, 2^21999240 is an apocalyptic number.

21999240 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 21999240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36454860).

21999240 is an abundant number, since it is smaller than the sum of its proper divisors (50910480).

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

21999240 is a wasteful number, since it uses less digits than its factorization.

21999240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1223 (or 1216 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 21999240 is about 4690.3347428515. The cubic root of 21999240 is about 280.2007064376.

The spelling of 21999240 in words is "twenty-one million, nine hundred ninety-nine thousand, two hundred forty".