21394563881 has 2 divisors, whose sum is σ = 21394563882. Its totient is φ = 21394563880.

The previous prime is 21394563809. The next prime is 21394563917. The reversal of 21394563881 is 18836549312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11376355600 + 10018208281 = 106660^2 + 100091^2 .

It is a cyclic number.

It is not a de Polignac number, because 21394563881 - 2¹⁴ = 21394547497 is a prime.

It is a super-2 number, since 2×21394563881² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21394593881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10697281940 + 10697281941.

It is an arithmetic number, because the mean of its divisors is an integer number (10697281941).

Almost surely, 2^21394563881 is an apocalyptic number.

It is an amenable number.

21394563881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21394563881 is an equidigital number, since it uses as much as digits as its factorization.

21394563881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1244160, while the sum is 50.

The spelling of 21394563881 in words is "twenty-one billion, three hundred ninety-four million, five hundred sixty-three thousand, eight hundred eighty-one".