81700649 has 2 divisors, whose sum is σ = 81700650. Its totient is φ = 81700648.

The previous prime is 81700637. The next prime is 81700673. The reversal of 81700649 is 94600718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 60171049 + 21529600 = 7757^2 + 4640^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81700649 is a prime.

It is not a weakly prime, because it can be changed into another prime (81700609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40850324 + 40850325.

It is an arithmetic number, because the mean of its divisors is an integer number (40850325).

Almost surely, 2^81700649 is an apocalyptic number.

It is an amenable number.

81700649 is a deficient number, since it is larger than the sum of its proper divisors (1).

81700649 is an equidigital number, since it uses as much as digits as its factorization.

81700649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 81700649 is about 9038.8411314726. The cubic root of 81700649 is about 433.9188352965.

The spelling of 81700649 in words is "eighty-one million, seven hundred thousand, six hundred forty-nine".