21247940 has 24 divisors (see below), whose sum is σ = 50995392. Its totient is φ = 7284960.

The previous prime is 21247937. The next prime is 21247979. The reversal of 21247940 is 4974212.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 75746 + ... + 76025.

It is an arithmetic number, because the mean of its divisors is an integer number (2124808).

Almost surely, 2^21247940 is an apocalyptic number.

21247940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21247940 is an abundant number, since it is smaller than the sum of its proper divisors (29747452).

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

21247940 is a wasteful number, since it uses less digits than its factorization.

21247940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151787 (or 151785 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21247940 is about 4609.5487848595. The cubic root of 21247940 is about 276.9739621987.

The spelling of 21247940 in words is "twenty-one million, two hundred forty-seven thousand, nine hundred forty".