81561706 has 8 divisors (see below), whose sum is σ = 123164100. Its totient is φ = 40507008.

The previous prime is 81561691. The next prime is 81561721. The reversal of 81561706 is 60716518.

It is an interprime number because it is at equal distance from previous prime (81561691) and next prime (81561721).

It can be written as a sum of positive squares in 2 ways, for example, as 61230625 + 20331081 = 7825^2 + 4509^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136551 + ... + 137146.

Almost surely, 2^81561706 is an apocalyptic number.

81561706 is a deficient number, since it is larger than the sum of its proper divisors (41602394).

81561706 is a wasteful number, since it uses less digits than its factorization.

81561706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273848.

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

The square root of 81561706 is about 9031.1519752466. The cubic root of 81561706 is about 433.6727165085.

The spelling of 81561706 in words is "eighty-one million, five hundred sixty-one thousand, seven hundred six".