20505551 has 8 divisors (see below), whose sum is σ = 22704384. Its totient is φ = 18362520.

The previous prime is 20505497. The next prime is 20505571. The reversal of 20505551 is 15550502.

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

It is not a de Polignac number, because 20505551 - 2⁶ = 20505487 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 (20505571) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13175 + ... + 14648.

It is an arithmetic number, because the mean of its divisors is an integer number (2838048).

Almost surely, 2^20505551 is an apocalyptic number.

20505551 is a deficient number, since it is larger than the sum of its proper divisors (2198833).

20505551 is a wasteful number, since it uses less digits than its factorization.

20505551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27901.

The product of its (nonzero) digits is 1250, while the sum is 23.

The square root of 20505551 is about 4528.3055329781. The cubic root of 20505551 is about 273.7098843798.

The spelling of 20505551 in words is "twenty million, five hundred five thousand, five hundred fifty-one".