21507764 has 24 divisors (see below), whose sum is σ = 38683008. Its totient is φ = 10458560.

The previous prime is 21507751. The next prime is 21507779. The reversal of 21507764 is 46770512.

It is a self number, because there is not a number n which added to its sum of digits gives 21507764.

It is a congruent number.

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, 43559 + ... + 44049.

It is an arithmetic number, because the mean of its divisors is an integer number (1611792).

Almost surely, 2^21507764 is an apocalyptic number.

It is an amenable number.

21507764 is a deficient number, since it is larger than the sum of its proper divisors (17175244).

21507764 is a wasteful number, since it uses less digits than its factorization.

21507764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 775 (or 773 counting only the distinct ones).

The product of its (nonzero) digits is 11760, while the sum is 32.

The square root of 21507764 is about 4637.6463858298. The cubic root of 21507764 is about 278.0983555505.

The spelling of 21507764 in words is "twenty-one million, five hundred seven thousand, seven hundred sixty-four".