20957509 has 2 divisors, whose sum is σ = 20957510. Its totient is φ = 20957508.

The previous prime is 20957491. The next prime is 20957527. The reversal of 20957509 is 90575902.

It is a balanced prime because it is at equal distance from previous prime (20957491) and next prime (20957527).

It can be written as a sum of positive squares in only one way, i.e., 17430625 + 3526884 = 4175^2 + 1878^2 .

It is a cyclic number.

It is not a de Polignac number, because 20957509 - 2¹³ = 20949317 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20957009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10478754 + 10478755.

It is an arithmetic number, because the mean of its divisors is an integer number (10478755).

Almost surely, 2^20957509 is an apocalyptic number.

It is an amenable number.

20957509 is a deficient number, since it is larger than the sum of its proper divisors (1).

20957509 is an equidigital number, since it uses as much as digits as its factorization.

20957509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28350, while the sum is 37.

The square root of 20957509 is about 4577.9371992198. The cubic root of 20957509 is about 275.7062135067.

It can be divided in two parts, 2095 and 7509, that added together give a square (9604 = 98²).

The spelling of 20957509 in words is "twenty million, nine hundred fifty-seven thousand, five hundred nine".