21346981 has 2 divisors, whose sum is σ = 21346982. Its totient is φ = 21346980.

The previous prime is 21346979. The next prime is 21346991. The reversal of 21346981 is 18964312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20784481 + 562500 = 4559^2 + 750^2 .

It is a cyclic number.

It is not a de Polignac number, because 21346981 - 2¹ = 21346979 is a prime.

It is a super-2 number, since 2×21346981² = 911387195628722, which contains 22 as substring.

Together with 21346979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21346961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10673490 + 10673491.

It is an arithmetic number, because the mean of its divisors is an integer number (10673491).

Almost surely, 2^21346981 is an apocalyptic number.

It is an amenable number.

21346981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21346981 is an equidigital number, since it uses as much as digits as its factorization.

21346981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 34.

The square root of 21346981 is about 4620.2793205606. The cubic root of 21346981 is about 277.4036394052.

It can be divided in two parts, 2 and 1346981, that multiplied together give a palindrome (2693962).

The spelling of 21346981 in words is "twenty-one million, three hundred forty-six thousand, nine hundred eighty-one".