20685551 has 2 divisors, whose sum is σ = 20685552. Its totient is φ = 20685550.

The previous prime is 20685523. The next prime is 20685557. The reversal of 20685551 is 15558602.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20685551 - 2¹⁴ = 20669167 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20685557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10342775 + 10342776.

It is an arithmetic number, because the mean of its divisors is an integer number (10342776).

Almost surely, 2^20685551 is an apocalyptic number.

20685551 is a deficient number, since it is larger than the sum of its proper divisors (1).

20685551 is an equidigital number, since it uses as much as digits as its factorization.

20685551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12000, while the sum is 32.

The square root of 20685551 is about 4548.1370911616. The cubic root of 20685551 is about 274.5084375583.

The spelling of 20685551 in words is "twenty million, six hundred eighty-five thousand, five hundred fifty-one".