20521765 has 16 divisors (see below), whose sum is σ = 27270720. Its totient is φ = 14699520.

The previous prime is 20521747. The next prime is 20521777. The reversal of 20521765 is 56712502.

It is not a de Polignac number, because 20521765 - 2⁵ = 20521733 is a prime.

It is a super-2 number, since 2×20521765² = 842285677430450, which contains 22 as substring.

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 15 ways as a sum of consecutive naturals, for example, 901 + ... + 6469.

It is an arithmetic number, because the mean of its divisors is an integer number (1704420).

Almost surely, 2^20521765 is an apocalyptic number.

It is an amenable number.

20521765 is a deficient number, since it is larger than the sum of its proper divisors (6748955).

20521765 is a wasteful number, since it uses less digits than its factorization.

20521765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5652.

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 20521765 is about 4530.0954736076. The cubic root of 20521765 is about 273.7820073359.

The spelling of 20521765 in words is "twenty million, five hundred twenty-one thousand, seven hundred sixty-five".