81620101 has 2 divisors, whose sum is σ = 81620102. Its totient is φ = 81620100.

The previous prime is 81620093. The next prime is 81620107. The reversal of 81620101 is 10102618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77616100 + 4004001 = 8810^2 + 2001^2 .

It is a cyclic number.

It is not a de Polignac number, because 81620101 - 2³ = 81620093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81620107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40810050 + 40810051.

It is an arithmetic number, because the mean of its divisors is an integer number (40810051).

Almost surely, 2^81620101 is an apocalyptic number.

It is an amenable number.

81620101 is a deficient number, since it is larger than the sum of its proper divisors (1).

81620101 is an equidigital number, since it uses as much as digits as its factorization.

81620101 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 81620101 is about 9034.3843730494. The cubic root of 81620101 is about 433.7761894011.

Adding to 81620101 its reverse (10102618), we get a palindrome (91722719).

The spelling of 81620101 in words is "eighty-one million, six hundred twenty thousand, one hundred one".