81361969 has 8 divisors (see below), whose sum is σ = 87999912. Its totient is φ = 74778240.

The previous prime is 81361963. The next prime is 81361981. The reversal of 81361969 is 96916318.

It can be written as a sum of positive squares in 4 ways, for example, as 5880625 + 75481344 = 2425^2 + 8688^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81361969 - 2⁵ = 81361937 is a prime.

It is a super-2 number, since 2×81361969² = 13239539999113922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81361963) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10402 + ... + 16459.

It is an arithmetic number, because the mean of its divisors is an integer number (10999989).

Almost surely, 2^81361969 is an apocalyptic number.

It is an amenable number.

81361969 is a deficient number, since it is larger than the sum of its proper divisors (6637943).

81361969 is a wasteful number, since it uses less digits than its factorization.

81361969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27107.

The product of its digits is 69984, while the sum is 43.

The square root of 81361969 is about 9020.0869729732. The cubic root of 81361969 is about 433.3184191448.

The spelling of 81361969 in words is "eighty-one million, three hundred sixty-one thousand, nine hundred sixty-nine".