20557551 has 8 divisors (see below), whose sum is σ = 31325824. Its totient is φ = 11747160.

The previous prime is 20557507. The next prime is 20557571. The reversal of 20557551 is 15575502.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20557551 - 2⁹ = 20557039 is a prime.

It is a super-2 number, since 2×20557551² = 845225806235202, which contains 22 as substring.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20557571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 489445 + ... + 489486.

It is an arithmetic number, because the mean of its divisors is an integer number (3915728).

Almost surely, 2^20557551 is an apocalyptic number.

20557551 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

20557551 is a deficient number, since it is larger than the sum of its proper divisors (10768273).

20557551 is an equidigital number, since it uses as much as digits as its factorization.

20557551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 978941.

The product of its (nonzero) digits is 8750, while the sum is 30.

The square root of 20557551 is about 4534.0435595614. The cubic root of 20557551 is about 273.9410559266.

The spelling of 20557551 in words is "twenty million, five hundred fifty-seven thousand, five hundred fifty-one".