21020420255 has 16 divisors (see below), whose sum is σ = 25434393600. Its totient is φ = 16676681760.

The previous prime is 21020420249. The next prime is 21020420261. The reversal of 21020420255 is 55202402012.

It is an interprime number because it is at equal distance from previous prime (21020420249) and next prime (21020420261).

It is not a de Polignac number, because 21020420255 - 2⁶ = 21020420191 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21020420255.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 622250 + ... + 655160.

It is an arithmetic number, because the mean of its divisors is an integer number (1589649600).

Almost surely, 2^21020420255 is an apocalyptic number.

21020420255 is a deficient number, since it is larger than the sum of its proper divisors (4413973345).

21020420255 is a wasteful number, since it uses less digits than its factorization.

21020420255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33974.

The product of its (nonzero) digits is 1600, while the sum is 23.

Adding to 21020420255 its reverse (55202402012), we get a palindrome (76222822267).

The spelling of 21020420255 in words is "twenty-one billion, twenty million, four hundred twenty thousand, two hundred fifty-five".