19999999961 has 4 divisors (see below), whose sum is σ = 20001245712. Its totient is φ = 19998754212.

The previous prime is 19999999939. The next prime is 19999999967. The reversal of 19999999961 is 16999999991.

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.

It is a cyclic number.

It is not a de Polignac number, because 19999999961 - 2¹⁸ = 19999737817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19999999967) 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, 598475 + ... + 631008.

It is an arithmetic number, because the mean of its divisors is an integer number (5000311428).

Almost surely, 2^19999999961 is an apocalyptic number.

It is an amenable number.

19999999961 is a deficient number, since it is larger than the sum of its proper divisors (1245751).

19999999961 is a wasteful number, since it uses less digits than its factorization.

19999999961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1245750.

The product of its digits is 258280326, while the sum is 80.

The spelling of 19999999961 in words is "nineteen billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, nine hundred sixty-one".