81010621 has 2 divisors, whose sum is σ = 81010622. Its totient is φ = 81010620.

The previous prime is 81010619. The next prime is 81010639. The reversal of 81010621 is 12601018.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 57836025 + 23174596 = 7605^2 + 4814^2 .

It is a cyclic number.

It is not a de Polignac number, because 81010621 - 2¹ = 81010619 is a prime.

Together with 81010619, 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 (81010651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40505310 + 40505311.

It is an arithmetic number, because the mean of its divisors is an integer number (40505311).

Almost surely, 2^81010621 is an apocalyptic number.

It is an amenable number.

81010621 is a deficient number, since it is larger than the sum of its proper divisors (1).

81010621 is an equidigital number, since it uses as much as digits as its factorization.

81010621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 19.

The square root of 81010621 is about 9000.5900362143. The cubic root of 81010621 is about 432.6937815406.

Adding to 81010621 its reverse (12601018), we get a palindrome (93611639).

The spelling of 81010621 in words is "eighty-one million, ten thousand, six hundred twenty-one".