21011020020 has 72 divisors (see below), whose sum is σ = 64935974376. Its totient is φ = 5497220352.

The previous prime is 21011019973. The next prime is 21011020061. The reversal of 21011020020 is 2002011012.

It can be written as a sum of positive squares in 4 ways, for example, as 7171379856 + 13839640164 = 84684^2 + 117642^2 .

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21011019984 and 21011020011.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1091667 + ... + 1110746.

It is an arithmetic number, because the mean of its divisors is an integer number (901888533).

Almost surely, 2^21011020020 is an apocalyptic number.

21011020020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21011020020 is an abundant number, since it is smaller than the sum of its proper divisors (43924954356).

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

21011020020 is a wasteful number, since it uses less digits than its factorization.

21011020020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2202481 (or 2202476 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21011020020 its reverse (2002011012), we get a palindrome (23013031032).

It can be divided in two parts, 2101 and 1020020, that added together give a square (1022121 = 1011²).

The spelling of 21011020020 in words is "twenty-one billion, eleven million, twenty thousand, twenty".