21020420253 has 32 divisors (see below), whose sum is σ = 33938334720. Its totient is φ = 11297422080.

The previous prime is 21020420249. The next prime is 21020420261. The reversal of 21020420253 is 35202402012.

It is not a de Polignac number, because 21020420253 - 2² = 21020420249 is a prime.

It is a super-2 number, since 2×21020420253² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020420203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 527338 + ... + 565796.

It is an arithmetic number, because the mean of its divisors is an integer number (1060572960).

Almost surely, 2^21020420253 is an apocalyptic number.

It is an amenable number.

21020420253 is a deficient number, since it is larger than the sum of its proper divisors (12917914467).

21020420253 is a wasteful number, since it uses less digits than its factorization.

21020420253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40017.

The product of its (nonzero) digits is 960, while the sum is 21.

Adding to 21020420253 its reverse (35202402012), we get a palindrome (56222822265).

The spelling of 21020420253 in words is "twenty-one billion, twenty million, four hundred twenty thousand, two hundred fifty-three".