81563761 has 2 divisors, whose sum is σ = 81563762. Its totient is φ = 81563760.

The previous prime is 81563737. The next prime is 81563809. The reversal of 81563761 is 16736518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 61716736 + 19847025 = 7856^2 + 4455^2 .

It is a cyclic number.

It is not a de Polignac number, because 81563761 - 2⁷ = 81563633 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81563761.

It is not a weakly prime, because it can be changed into another prime (81560761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40781880 + 40781881.

It is an arithmetic number, because the mean of its divisors is an integer number (40781881).

Almost surely, 2^81563761 is an apocalyptic number.

It is an amenable number.

81563761 is a deficient number, since it is larger than the sum of its proper divisors (1).

81563761 is an equidigital number, since it uses as much as digits as its factorization.

81563761 is an evil number, because the sum of its binary digits is even.

The product of its digits is 30240, while the sum is 37.

The square root of 81563761 is about 9031.2657473911. The cubic root of 81563761 is about 433.6763586995.

The spelling of 81563761 in words is "eighty-one million, five hundred sixty-three thousand, seven hundred sixty-one".