81013778 has 4 divisors (see below), whose sum is σ = 121520670. Its totient is φ = 40506888.

The previous prime is 81013741. The next prime is 81013781. The reversal of 81013778 is 87731018.

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., 49463089 + 31550689 = 7033^2 + 5617^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20253443 + ... + 20253446.

Almost surely, 2^81013778 is an apocalyptic number.

81013778 is a deficient number, since it is larger than the sum of its proper divisors (40506892).

81013778 is a wasteful number, since it uses less digits than its factorization.

81013778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40506891.

The product of its (nonzero) digits is 9408, while the sum is 35.

The square root of 81013778 is about 9000.7654118969. The cubic root of 81013778 is about 432.6994021885.

The spelling of 81013778 in words is "eighty-one million, thirteen thousand, seven hundred seventy-eight".