21602421640781 has 2 divisors, whose sum is σ = 21602421640782. Its totient is φ = 21602421640780.

The previous prime is 21602421640771. The next prime is 21602421640831. The reversal of 21602421640781 is 18704612420612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19060724807881 + 2541696832900 = 4365859^2 + 1594270^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21602421640781 is a prime.

It is a super-2 number, since 2×21602421640781² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21602421640771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10801210820390 + 10801210820391.

It is an arithmetic number, because the mean of its divisors is an integer number (10801210820391).

Almost surely, 2^{21602421640781} is an apocalyptic number.

It is an amenable number.

21602421640781 is a deficient number, since it is larger than the sum of its proper divisors (1).

21602421640781 is an equidigital number, since it uses as much as digits as its factorization.

21602421640781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 258048, while the sum is 44.

The spelling of 21602421640781 in words is "twenty-one trillion, six hundred two billion, four hundred twenty-one million, six hundred forty thousand, seven hundred eighty-one".