21386430081 has 15 divisors (see below), whose sum is σ = 31949596371. Its totient is φ = 14256742608.

The previous prime is 21386430067. The next prime is 21386430089. The reversal of 21386430081 is 18003468312.

The square root of 21386430081 is 146241.

It is a perfect power (a square), and thus also a powerful number.

21386430081 is a `hidden beast` number, since 2 + 1 + 3 + 8 + 643 + 0 + 0 + 8 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 12759735681 + 8626694400 = 112959^2 + 92880^2 .

It is not a de Polignac number, because 21386430081 - 2²³ = 21378041473 is a prime.

It is a super-2 number, since 2×21386430081² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21386430089) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 1308045 + ... + 1324293.

Almost surely, 2^21386430081 is an apocalyptic number.

21386430081 is the 146241-st square number.

21386430081 is the 73121-st centered octagonal number.

It is an amenable number.

21386430081 is a deficient number, since it is larger than the sum of its proper divisors (10563166290).

21386430081 is an frugal number, since it uses more digits than its factorization.

21386430081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32510 (or 16252 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

Multiplying 21386430081 by its sum of digits (36), we get a square (769911482916 = 877446²).

Adding to 21386430081 its reverse (18003468312), we get a palindrome (39389898393).

The spelling of 21386430081 in words is "twenty-one billion, three hundred eighty-six million, four hundred thirty thousand, eighty-one".