21247740 has 36 divisors (see below), whose sum is σ = 64452024. Its totient is φ = 5666016.

The previous prime is 21247727. The next prime is 21247769. The reversal of 21247740 is 4774212.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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 11 ways as a sum of consecutive naturals, for example, 58842 + ... + 59201.

It is an arithmetic number, because the mean of its divisors is an integer number (1790334).

Almost surely, 2^21247740 is an apocalyptic number.

21247740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21247740 is an abundant number, since it is smaller than the sum of its proper divisors (43204284).

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

21247740 is a wasteful number, since it uses less digits than its factorization.

21247740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118058 (or 118053 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 27.

The square root of 21247740 is about 4609.5270907112. The cubic root of 21247740 is about 276.9730931738.

The spelling of 21247740 in words is "twenty-one million, two hundred forty-seven thousand, seven hundred forty".