21020012021 has 8 divisors (see below), whose sum is σ = 21942026424. Its totient is φ = 20116624320.

The previous prime is 21020011973. The next prime is 21020012059. The reversal of 21020012021 is 12021002012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 6188182225 + 14831829796 = 78665^2 + 121786^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020012021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21020011993 and 21020012011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020012081) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4654370 + ... + 4658883.

It is an arithmetic number, because the mean of its divisors is an integer number (2742753303).

Almost surely, 2^21020012021 is an apocalyptic number.

It is an amenable number.

21020012021 is a deficient number, since it is larger than the sum of its proper divisors (922014403).

21020012021 is an equidigital number, since it uses as much as digits as its factorization.

21020012021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9313351.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21020012021 its reverse (12021002012), we get a palindrome (33041014033).

The spelling of 21020012021 in words is "twenty-one billion, twenty million, twelve thousand, twenty-one".