20355551 has 4 divisors (see below), whose sum is σ = 20739672. Its totient is φ = 19971432.

The previous prime is 20355541. The next prime is 20355553. The reversal of 20355551 is 15555302.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20355551 - 2¹⁰ = 20354527 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 20355551.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20355553) 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, 191981 + ... + 192086.

It is an arithmetic number, because the mean of its divisors is an integer number (5184918).

Almost surely, 2^20355551 is an apocalyptic number.

20355551 is a deficient number, since it is larger than the sum of its proper divisors (384121).

20355551 is an equidigital number, since it uses as much as digits as its factorization.

20355551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384120.

The product of its (nonzero) digits is 3750, while the sum is 26.

The square root of 20355551 is about 4511.7126459915. The cubic root of 20355551 is about 273.0408459951.

The spelling of 20355551 in words is "twenty million, three hundred fifty-five thousand, five hundred fifty-one".