20697557 has 4 divisors (see below), whose sum is σ = 20707020. Its totient is φ = 20688096.

The previous prime is 20697511. The next prime is 20697559. The reversal of 20697557 is 75579602.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 13942756 + 6754801 = 3734^2 + 2599^2 .

It is a cyclic number.

It is not a de Polignac number, because 20697557 - 2⁸ = 20697301 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20697559) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 419 + ... + 6447.

It is an arithmetic number, because the mean of its divisors is an integer number (5176755).

Almost surely, 2^20697557 is an apocalyptic number.

It is an amenable number.

20697557 is a deficient number, since it is larger than the sum of its proper divisors (9463).

20697557 is an equidigital number, since it uses as much as digits as its factorization.

20697557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9462.

The product of its (nonzero) digits is 132300, while the sum is 41.

The square root of 20697557 is about 4549.4567807597. The cubic root of 20697557 is about 274.5615359889.

The spelling of 20697557 in words is "twenty million, six hundred ninety-seven thousand, five hundred fifty-seven".