99997781 has 4 divisors (see below), whose sum is σ = 107689932. Its totient is φ = 92305632.

The previous prime is 99997769. The next prime is 99997783. The reversal of 99997781 is 18779999.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 61371556 + 38626225 = 7834^2 + 6215^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-99997781 is a prime.

It is a super-2 number, since 2×99997781² = 19999112409847922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 99997781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99997783) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3846056 + ... + 3846081.

It is an arithmetic number, because the mean of its divisors is an integer number (26922483).

Almost surely, 2^99997781 is an apocalyptic number.

It is an amenable number.

99997781 is a deficient number, since it is larger than the sum of its proper divisors (7692151).

99997781 is a wasteful number, since it uses less digits than its factorization.

99997781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7692150.

The product of its digits is 2571912, while the sum is 59.

The square root of 99997781 is about 9999.8890493845. The cubic root of 99997781 is about 464.1554501073.

The spelling of 99997781 in words is "ninety-nine million, nine hundred ninety-seven thousand, seven hundred eighty-one".