81638426 has 4 divisors (see below), whose sum is σ = 122457642. Its totient is φ = 40819212.

The previous prime is 81638419. The next prime is 81638443. The reversal of 81638426 is 62483618.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 62483618 = 2 ⋅31241809.

It can be written as a sum of positive squares in only one way, i.e., 57775201 + 23863225 = 7601^2 + 4885^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81638426.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20409605 + ... + 20409608.

Almost surely, 2^81638426 is an apocalyptic number.

81638426 is a deficient number, since it is larger than the sum of its proper divisors (40819216).

81638426 is a wasteful number, since it uses less digits than its factorization.

81638426 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40819215.

The product of its digits is 55296, while the sum is 38.

The square root of 81638426 is about 9035.3984970227. The cubic root of 81638426 is about 433.8086501706.

The spelling of 81638426 in words is "eighty-one million, six hundred thirty-eight thousand, four hundred twenty-six".