21485840 has 20 divisors (see below), whose sum is σ = 49954764. Its totient is φ = 8594304.

The previous prime is 21485833. The next prime is 21485843. The reversal of 21485840 is 4858412.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5740816 + 15745024 = 2396^2 + 3968^2 .

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 21485797 and 21485806.

It is not an unprimeable number, because it can be changed into a prime (21485843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134207 + ... + 134366.

Almost surely, 2^21485840 is an apocalyptic number.

21485840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21485840 is an abundant number, since it is smaller than the sum of its proper divisors (28468924).

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

21485840 is a wasteful number, since it uses less digits than its factorization.

21485840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 268586 (or 268580 counting only the distinct ones).

The product of its (nonzero) digits is 10240, while the sum is 32.

The square root of 21485840 is about 4635.2820841886. The cubic root of 21485840 is about 278.0038299767.

The spelling of 21485840 in words is "twenty-one million, four hundred eighty-five thousand, eight hundred forty".