20851553 has 4 divisors (see below), whose sum is σ = 20928768. Its totient is φ = 20774340.

The previous prime is 20851549. The next prime is 20851573. The reversal of 20851553 is 35515802.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20851553 - 2² = 20851549 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20851513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38201 + ... + 38742.

It is an arithmetic number, because the mean of its divisors is an integer number (5232192).

Almost surely, 2^20851553 is an apocalyptic number.

It is an amenable number.

20851553 is a deficient number, since it is larger than the sum of its proper divisors (77215).

20851553 is an equidigital number, since it uses as much as digits as its factorization.

20851553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77214.

The product of its (nonzero) digits is 6000, while the sum is 29.

The square root of 20851553 is about 4566.3500741840. The cubic root of 20851553 is about 275.2407940543.

The spelling of 20851553 in words is "twenty million, eight hundred fifty-one thousand, five hundred fifty-three".