81619826 has 4 divisors (see below), whose sum is σ = 122429742. Its totient is φ = 40809912.

The previous prime is 81619819. The next prime is 81619829. The reversal of 81619826 is 62891618.

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., 60450625 + 21169201 = 7775^2 + 4601^2 .

It is not an unprimeable number, because it can be changed into a prime (81619829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20404955 + ... + 20404958.

Almost surely, 2^81619826 is an apocalyptic number.

81619826 is a deficient number, since it is larger than the sum of its proper divisors (40809916).

81619826 is a wasteful number, since it uses less digits than its factorization.

81619826 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40809915.

The product of its digits is 41472, while the sum is 41.

The square root of 81619826 is about 9034.3691534052. The cubic root of 81619826 is about 433.7757022311.

The spelling of 81619826 in words is "eighty-one million, six hundred nineteen thousand, eight hundred twenty-six".