21020420190 has 128 divisors (see below), whose sum is σ = 63176122368. Its totient is φ = 4348529280.

The previous prime is 21020420189. The next prime is 21020420191. The reversal of 21020420190 is 9102402012.

It is an interprime number because it is at equal distance from previous prime (21020420189) and next prime (21020420191).

It is a super-2 number, since 2×21020420190² (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 (21020420191) 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 63 ways as a sum of consecutive naturals, for example, 504327 + ... + 544413.

It is an arithmetic number, because the mean of its divisors is an integer number (493563456).

Almost surely, 2^21020420190 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21020420190, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31588061184).

21020420190 is an abundant number, since it is smaller than the sum of its proper divisors (42155702178).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21020420190 is a wasteful number, since it uses less digits than its factorization.

21020420190 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40342.

The product of its (nonzero) digits is 288, while the sum is 21.

The spelling of 21020420190 in words is "twenty-one billion, twenty million, four hundred twenty thousand, one hundred ninety".