21020420250 has 96 divisors (see below), whose sum is σ = 57391686144. Its totient is φ = 5550962400.

The previous prime is 21020420249. The next prime is 21020420261. The reversal of 21020420250 is 5202402012.

21020420250 is a `hidden beast` number, since 210 + 204 + 2 + 0 + 250 = 666.

It is a super-2 number, since 2×21020420250² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 186399 + ... + 277101.

It is an arithmetic number, because the mean of its divisors is an integer number (597830064).

Almost surely, 2^21020420250 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21020420250, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28695843072).

21020420250 is an abundant number, since it is smaller than the sum of its proper divisors (36371265894).

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

21020420250 is a wasteful number, since it uses less digits than its factorization.

21020420250 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90829 (or 90816 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

Adding to 21020420250 its reverse (5202402012), we get a palindrome (26222822262).

The spelling of 21020420250 in words is "twenty-one billion, twenty million, four hundred twenty thousand, two hundred fifty".