20711657 has 4 divisors (see below), whose sum is σ = 20895060. Its totient is φ = 20528256.

The previous prime is 20711651. The next prime is 20711659. The reversal of 20711657 is 75611702.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 75611702 = 2 ⋅37805851.

It can be written as a sum of positive squares in 2 ways, for example, as 7722841 + 12988816 = 2779^2 + 3604^2 .

It is a cyclic number.

It is not a de Polignac number, because 20711657 - 2⁴ = 20711641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20711651) 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 3 ways as a sum of consecutive naturals, for example, 91532 + ... + 91757.

It is an arithmetic number, because the mean of its divisors is an integer number (5223765).

Almost surely, 2^20711657 is an apocalyptic number.

It is an amenable number.

20711657 is a deficient number, since it is larger than the sum of its proper divisors (183403).

20711657 is a wasteful number, since it uses less digits than its factorization.

20711657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 183402.

The product of its (nonzero) digits is 2940, while the sum is 29.

The square root of 20711657 is about 4551.0061524898. The cubic root of 20711657 is about 274.6238692535.

The spelling of 20711657 in words is "twenty million, seven hundred eleven thousand, six hundred fifty-seven".