20387721 has 8 divisors (see below), whose sum is σ = 27566784. Its totient is φ = 13400240.

The previous prime is 20387713. The next prime is 20387747. The reversal of 20387721 is 12778302.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20387721 - 2³ = 20387713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20387711) 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 7 ways as a sum of consecutive naturals, for example, 47646 + ... + 48071.

It is an arithmetic number, because the mean of its divisors is an integer number (3445848).

Almost surely, 2^20387721 is an apocalyptic number.

It is an amenable number.

20387721 is a deficient number, since it is larger than the sum of its proper divisors (7179063).

20387721 is an equidigital number, since it uses as much as digits as its factorization.

20387721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95791.

The product of its (nonzero) digits is 4704, while the sum is 30.

The square root of 20387721 is about 4515.2764034996. The cubic root of 20387721 is about 273.1846085949.

The spelling of 20387721 in words is "twenty million, three hundred eighty-seven thousand, seven hundred twenty-one".