19909979 has 4 divisors (see below), whose sum is σ = 20596560. Its totient is φ = 19223400.

The previous prime is 19909951. The next prime is 19909993. The reversal of 19909979 is 97990991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97990991 = 7 ⋅13998713.

It is a cyclic number.

It is not a de Polignac number, because 19909979 - 2²⁴ = 3132763 is a prime.

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 19909979.

It is not an unprimeable number, because it can be changed into a prime (19909919) 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, 343247 + ... + 343304.

It is an arithmetic number, because the mean of its divisors is an integer number (5149140).

Almost surely, 2^19909979 is an apocalyptic number.

19909979 is a deficient number, since it is larger than the sum of its proper divisors (686581).

19909979 is an equidigital number, since it uses as much as digits as its factorization.

19909979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 686580.

The product of its (nonzero) digits is 413343, while the sum is 53.

The square root of 19909979 is about 4462.0599502920. The cubic root of 19909979 is about 271.0338914508.

The spelling of 19909979 in words is "nineteen million, nine hundred nine thousand, nine hundred seventy-nine".