81570661 has 4 divisors (see below), whose sum is σ = 81672300. Its totient is φ = 81469024.

The previous prime is 81570637. The next prime is 81570677. The reversal of 81570661 is 16607518.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 34222500 + 47348161 = 5850^2 + 6881^2 .

It is a cyclic number.

It is not a de Polignac number, because 81570661 - 2¹⁵ = 81537893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81570631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 49606 + ... + 51223.

It is an arithmetic number, because the mean of its divisors is an integer number (20418075).

Almost surely, 2^81570661 is an apocalyptic number.

It is an amenable number.

81570661 is a deficient number, since it is larger than the sum of its proper divisors (101639).

81570661 is a wasteful number, since it uses less digits than its factorization.

81570661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101638.

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 81570661 is about 9031.6477455667. The cubic root of 81570661 is about 433.6885875066.

The spelling of 81570661 in words is "eighty-one million, five hundred seventy thousand, six hundred sixty-one".