81436661 has 2 divisors, whose sum is σ = 81436662. Its totient is φ = 81436660.

The previous prime is 81436657. The next prime is 81436723. The reversal of 81436661 is 16663418.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73427761 + 8008900 = 8569^2 + 2830^2 .

It is a cyclic number.

It is not a de Polignac number, because 81436661 - 2² = 81436657 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81436631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40718330 + 40718331.

It is an arithmetic number, because the mean of its divisors is an integer number (40718331).

Almost surely, 2^81436661 is an apocalyptic number.

It is an amenable number.

81436661 is a deficient number, since it is larger than the sum of its proper divisors (1).

81436661 is an equidigital number, since it uses as much as digits as its factorization.

81436661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 35.

The square root of 81436661 is about 9024.2263380303. The cubic root of 81436661 is about 433.4509770658.

The spelling of 81436661 in words is "eighty-one million, four hundred thirty-six thousand, six hundred sixty-one".