21355940 has 12 divisors (see below), whose sum is σ = 44847516. Its totient is φ = 8542368.

The previous prime is 21355921. The next prime is 21355949. The reversal of 21355940 is 4955312.

It can be written as a sum of positive squares in 2 ways, for example, as 13380964 + 7974976 = 3658^2 + 2824^2 .

It is not an unprimeable number, because it can be changed into a prime (21355949) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 533879 + ... + 533918.

It is an arithmetic number, because the mean of its divisors is an integer number (3737293).

Almost surely, 2^21355940 is an apocalyptic number.

21355940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21355940 is an abundant number, since it is smaller than the sum of its proper divisors (23491576).

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

21355940 is a wasteful number, since it uses less digits than its factorization.

21355940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1067806 (or 1067804 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 21355940 is about 4621.2487489855. The cubic root of 21355940 is about 277.4424413262.

The spelling of 21355940 in words is "twenty-one million, three hundred fifty-five thousand, nine hundred forty".