20720785 has 16 divisors (see below), whose sum is σ = 25904592. Its totient is φ = 15897600.

The previous prime is 20720771. The next prime is 20720789. The reversal of 20720785 is 58702702.

It can be written as a sum of positive squares in 8 ways, for example, as 9585216 + 11135569 = 3096^2 + 3337^2 .

It is not a de Polignac number, because 20720785 - 2⁵ = 20720753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20720789) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 11677 + ... + 13333.

It is an arithmetic number, because the mean of its divisors is an integer number (1619037).

Almost surely, 2^20720785 is an apocalyptic number.

It is an amenable number.

20720785 is a deficient number, since it is larger than the sum of its proper divisors (5183807).

20720785 is a wasteful number, since it uses less digits than its factorization.

20720785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1764.

The product of its (nonzero) digits is 7840, while the sum is 31.

The square root of 20720785 is about 4552.0088971794. The cubic root of 20720785 is about 274.6642072221.

The spelling of 20720785 in words is "twenty million, seven hundred twenty thousand, seven hundred eighty-five".