21020002001 has 2 divisors, whose sum is σ = 21020002002. Its totient is φ = 21020002000.

The previous prime is 21020001973. The next prime is 21020002063. The reversal of 21020002001 is 10020002012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20506526401 + 513475600 = 143201^2 + 22660^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020002001 - 2¹⁴ = 21019985617 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21020002001.

It is not a weakly prime, because it can be changed into another prime (21020802001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510001000 + 10510001001.

It is an arithmetic number, because the mean of its divisors is an integer number (10510001001).

Almost surely, 2^21020002001 is an apocalyptic number.

It is an amenable number.

21020002001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020002001 is an equidigital number, since it uses as much as digits as its factorization.

21020002001 is an evil number, because the sum of its binary digits is even.

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

Adding to 21020002001 its reverse (10020002012), we get a palindrome (31040004013).

The spelling of 21020002001 in words is "twenty-one billion, twenty million, two thousand, one".