21502036021 has 2 divisors, whose sum is σ = 21502036022. Its totient is φ = 21502036020.

The previous prime is 21502036019. The next prime is 21502036057. The reversal of 21502036021 is 12063020512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13250312100 + 8251723921 = 115110^2 + 90839^2 .

It is a cyclic number.

It is not a de Polignac number, because 21502036021 - 2¹ = 21502036019 is a prime.

Together with 21502036019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21502035983 and 21502036001.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21502036091) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10751018010 + 10751018011.

It is an arithmetic number, because the mean of its divisors is an integer number (10751018011).

Almost surely, 2^21502036021 is an apocalyptic number.

It is an amenable number.

21502036021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21502036021 is an equidigital number, since it uses as much as digits as its factorization.

21502036021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 22.

Adding to 21502036021 its reverse (12063020512), we get a palindrome (33565056533).

The spelling of 21502036021 in words is "twenty-one billion, five hundred two million, thirty-six thousand, twenty-one".