99999781 has 8 divisors (see below), whose sum is σ = 114396224. Its totient is φ = 85631040.

The previous prime is 99999773. The next prime is 99999787. The reversal of 99999781 is 18799999.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 99999781 - 2³ = 99999773 is a prime.

It is a super-2 number, since 2×99999781² = 19999912400095922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99999787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1501 + ... + 14221.

It is an arithmetic number, because the mean of its divisors is an integer number (14299528).

Almost surely, 2^99999781 is an apocalyptic number.

It is an amenable number.

99999781 is a deficient number, since it is larger than the sum of its proper divisors (14396443).

99999781 is a wasteful number, since it uses less digits than its factorization.

99999781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13851.

The product of its digits is 3306744, while the sum is 61.

The square root of 99999781 is about 9999.9890499940. The cubic root of 99999781 is about 464.1585445250.

The spelling of 99999781 in words is "ninety-nine million, nine hundred ninety-nine thousand, seven hundred eighty-one".