81361642 has 4 divisors (see below), whose sum is σ = 122042466. Its totient is φ = 40680820.

The previous prime is 81361627. The next prime is 81361691. The reversal of 81361642 is 24616318.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 71757841 + 9603801 = 8471^2 + 3099^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20340409 + ... + 20340412.

Almost surely, 2^81361642 is an apocalyptic number.

81361642 is a deficient number, since it is larger than the sum of its proper divisors (40680824).

81361642 is a wasteful number, since it uses less digits than its factorization.

81361642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40680823.

The product of its digits is 6912, while the sum is 31.

The square root of 81361642 is about 9020.0688467439. The cubic root of 81361642 is about 433.3178386307.

The spelling of 81361642 in words is "eighty-one million, three hundred sixty-one thousand, six hundred forty-two".