81738421 has 2 divisors, whose sum is σ = 81738422. Its totient is φ = 81738420.

The previous prime is 81738409. The next prime is 81738463. The reversal of 81738421 is 12483718.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64224196 + 17514225 = 8014^2 + 4185^2 .

It is a cyclic number.

It is not a de Polignac number, because 81738421 - 2¹⁵ = 81705653 is a prime.

It is equal to p_4765039 and since 81738421 and 4765039 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81738491) 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 as a sum of consecutive naturals, namely, 40869210 + 40869211.

It is an arithmetic number, because the mean of its divisors is an integer number (40869211).

Almost surely, 2^81738421 is an apocalyptic number.

It is an amenable number.

81738421 is a deficient number, since it is larger than the sum of its proper divisors (1).

81738421 is an equidigital number, since it uses as much as digits as its factorization.

81738421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10752, while the sum is 34.

The square root of 81738421 is about 9040.9303171742. The cubic root of 81738421 is about 433.9856950554.

The spelling of 81738421 in words is "eighty-one million, seven hundred thirty-eight thousand, four hundred twenty-one".