99978509 has 4 divisors (see below), whose sum is σ = 101673120. Its totient is φ = 98283900.

The previous prime is 99978499. The next prime is 99978517. The reversal of 99978509 is 90587999.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 90587999 = 4993 ⋅18143.

It is a cyclic number.

It is not a de Polignac number, because 99978509 - 2¹⁶ = 99912973 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99978559) 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, 847217 + ... + 847334.

It is an arithmetic number, because the mean of its divisors is an integer number (25418280).

Almost surely, 2^99978509 is an apocalyptic number.

It is an amenable number.

99978509 is a deficient number, since it is larger than the sum of its proper divisors (1694611).

99978509 is a wasteful number, since it uses less digits than its factorization.

99978509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1694610.

The product of its (nonzero) digits is 1837080, while the sum is 56.

The square root of 99978509 is about 9998.9253922609. The cubic root of 99978509 is about 464.1256301838.

The spelling of 99978509 in words is "ninety-nine million, nine hundred seventy-eight thousand, five hundred nine".