21613430381 has 2 divisors, whose sum is σ = 21613430382. Its totient is φ = 21613430380.

The previous prime is 21613430347. The next prime is 21613430389. The reversal of 21613430381 is 18303431612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13429333225 + 8184097156 = 115885^2 + 90466^2 .

It is a cyclic number.

It is not a de Polignac number, because 21613430381 - 2³⁰ = 20539688557 is a prime.

It is a super-2 number, since 2×21613430381² (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 (21613430389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10806715190 + 10806715191.

It is an arithmetic number, because the mean of its divisors is an integer number (10806715191).

Almost surely, 2^21613430381 is an apocalyptic number.

It is an amenable number.

21613430381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21613430381 is an equidigital number, since it uses as much as digits as its factorization.

21613430381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10368, while the sum is 32.

Adding to 21613430381 its reverse (18303431612), we get a palindrome (39916861993).

The spelling of 21613430381 in words is "twenty-one billion, six hundred thirteen million, four hundred thirty thousand, three hundred eighty-one".