81621349 has 2 divisors, whose sum is σ = 81621350. Its totient is φ = 81621348.

The previous prime is 81621347. The next prime is 81621361. The reversal of 81621349 is 94312618.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 81324324 + 297025 = 9018^2 + 545^2 .

It is a cyclic number.

It is not a de Polignac number, because 81621349 - 2¹ = 81621347 is a prime.

It is a super-2 number, since 2×81621349² = 13324089225159602, which contains 22 as substring.

Together with 81621347, it forms a pair of twin primes.

It is equal to p_4758622 and since 81621349 and 4758622 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 (81621347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40810674 + 40810675.

It is an arithmetic number, because the mean of its divisors is an integer number (40810675).

Almost surely, 2^81621349 is an apocalyptic number.

It is an amenable number.

81621349 is a deficient number, since it is larger than the sum of its proper divisors (1).

81621349 is an equidigital number, since it uses as much as digits as its factorization.

81621349 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 81621349 is about 9034.4534422399. The cubic root of 81621349 is about 433.7784002532.

The spelling of 81621349 in words is "eighty-one million, six hundred twenty-one thousand, three hundred forty-nine".