21202018020 has 36 divisors (see below), whose sum is σ = 64312788540. Its totient is φ = 5653871424.

The previous prime is 21202018003. The next prime is 21202018021. The reversal of 21202018020 is 2081020212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 3434194404 + 17767823616 = 58602^2 + 133296^2 .

It is a tau number, because it is divible by the number of its divisors (36).

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

It is a junction number, because it is equal to n+sod(n) for n = 21202017984 and 21202018002.

It is not an unprimeable number, because it can be changed into a prime (21202018021) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 58894315 + ... + 58894674.

Almost surely, 2^21202018020 is an apocalyptic number.

21202018020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21202018020 is an abundant number, since it is smaller than the sum of its proper divisors (43110770520).

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

21202018020 is a wasteful number, since it uses less digits than its factorization.

21202018020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117789004 (or 117788999 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

Adding to 21202018020 its reverse (2081020212), we get a palindrome (23283038232).

The spelling of 21202018020 in words is "twenty-one billion, two hundred two million, eighteen thousand, twenty".