20420551 has 4 divisors (see below), whose sum is σ = 20493504. Its totient is φ = 20347600.

The previous prime is 20420531. The next prime is 20420557. The reversal of 20420551 is 15502402.

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-20420551 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 (20420557) 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, 36055 + ... + 36616.

It is an arithmetic number, because the mean of its divisors is an integer number (5123376).

Almost surely, 2^20420551 is an apocalyptic number.

20420551 is a deficient number, since it is larger than the sum of its proper divisors (72953).

20420551 is an equidigital number, since it uses as much as digits as its factorization.

20420551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72952.

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 20420551 is about 4518.9103775136. The cubic root of 20420551 is about 273.3311647987.

Adding to 20420551 its reverse (15502402), we get a palindrome (35922953).

The spelling of 20420551 in words is "twenty million, four hundred twenty thousand, five hundred fifty-one".