81651494 has 4 divisors (see below), whose sum is σ = 122477244. Its totient is φ = 40825746.

The previous prime is 81651481. The next prime is 81651497. The reversal of 81651494 is 49415618.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81651497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20412872 + ... + 20412875.

It is an arithmetic number, because the mean of its divisors is an integer number (30619311).

Almost surely, 2^81651494 is an apocalyptic number.

81651494 is a deficient number, since it is larger than the sum of its proper divisors (40825750).

81651494 is a wasteful number, since it uses less digits than its factorization.

81651494 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40825749.

The product of its digits is 34560, while the sum is 38.

The square root of 81651494 is about 9036.1216237941. The cubic root of 81651494 is about 433.8317957621.

The spelling of 81651494 in words is "eighty-one million, six hundred fifty-one thousand, four hundred ninety-four".