20420355551 has 4 divisors (see below), whose sum is σ = 20421403272. Its totient is φ = 20419307832.

The previous prime is 20420355427. The next prime is 20420355559. The reversal of 20420355551 is 15555302402.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20420355551 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 (20420355559) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 494060 + ... + 533793.

It is an arithmetic number, because the mean of its divisors is an integer number (5105350818).

Almost surely, 2^20420355551 is an apocalyptic number.

20420355551 is a deficient number, since it is larger than the sum of its proper divisors (1047721).

20420355551 is a wasteful number, since it uses less digits than its factorization.

20420355551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1047720.

The product of its (nonzero) digits is 30000, while the sum is 32.

Adding to 20420355551 its reverse (15555302402), we get a palindrome (35975657953).

The spelling of 20420355551 in words is "twenty billion, four hundred twenty million, three hundred fifty-five thousand, five hundred fifty-one".