21509300381 has 2 divisors, whose sum is σ = 21509300382. Its totient is φ = 21509300380.

The previous prime is 21509300357. The next prime is 21509300399. The reversal of 21509300381 is 18300390512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17309612356 + 4199688025 = 131566^2 + 64805^2 .

It is a cyclic number.

It is not a de Polignac number, because 21509300381 - 2¹⁴ = 21509283997 is a prime.

It is a super-2 number, since 2×21509300381² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21509300581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10754650190 + 10754650191.

It is an arithmetic number, because the mean of its divisors is an integer number (10754650191).

Almost surely, 2^21509300381 is an apocalyptic number.

It is an amenable number.

21509300381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21509300381 is an equidigital number, since it uses as much as digits as its factorization.

21509300381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6480, while the sum is 32.

Adding to 21509300381 its reverse (18300390512), we get a palindrome (39809690893).

The spelling of 21509300381 in words is "twenty-one billion, five hundred nine million, three hundred thousand, three hundred eighty-one".