21657683381 has 2 divisors, whose sum is σ = 21657683382. Its totient is φ = 21657683380.

The previous prime is 21657683371. The next prime is 21657683441. The reversal of 21657683381 is 18338675612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17316191281 + 4341492100 = 131591^2 + 65890^2 .

It is a cyclic number.

It is not a de Polignac number, because 21657683381 - 2³⁰ = 20583941557 is a prime.

It is a super-2 number, since 2×21657683381² (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 (21657683371) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10828841690 + 10828841691.

It is an arithmetic number, because the mean of its divisors is an integer number (10828841691).

Almost surely, 2^21657683381 is an apocalyptic number.

It is an amenable number.

21657683381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21657683381 is an equidigital number, since it uses as much as digits as its factorization.

21657683381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1451520, while the sum is 50.

The spelling of 21657683381 in words is "twenty-one billion, six hundred fifty-seven million, six hundred eighty-three thousand, three hundred eighty-one".