81337778 has 4 divisors (see below), whose sum is σ = 122006670. Its totient is φ = 40668888.

The previous prime is 81337771. The next prime is 81337783. The reversal of 81337778 is 87773318.

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., 80156209 + 1181569 = 8953^2 + 1087^2 .

It is not an unprimeable number, because it can be changed into a prime (81337771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20334443 + ... + 20334446.

Almost surely, 2^81337778 is an apocalyptic number.

81337778 is a deficient number, since it is larger than the sum of its proper divisors (40668892).

81337778 is a wasteful number, since it uses less digits than its factorization.

81337778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40668891.

The product of its digits is 197568, while the sum is 44.

The square root of 81337778 is about 9018.7459216900. The cubic root of 81337778 is about 433.2754693282.

The spelling of 81337778 in words is "eighty-one million, three hundred thirty-seven thousand, seven hundred seventy-eight".