19651021961 has 4 divisors (see below), whose sum is σ = 19973169924. Its totient is φ = 19328874000.

The previous prime is 19651021921. The next prime is 19651021991. The reversal of 19651021961 is 16912015691.

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 1736805625 + 17914216336 = 41675^2 + 133844^2 .

It is a cyclic number.

It is not a de Polignac number, because 19651021961 - 2²² = 19646827657 is a prime.

It is a super-2 number, since 2×19651021961² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19651021921) 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, 161073890 + ... + 161074011.

It is an arithmetic number, because the mean of its divisors is an integer number (4993292481).

Almost surely, 2^19651021961 is an apocalyptic number.

It is an amenable number.

19651021961 is a deficient number, since it is larger than the sum of its proper divisors (322147963).

19651021961 is an equidigital number, since it uses as much as digits as its factorization.

19651021961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322147962.

The product of its (nonzero) digits is 29160, while the sum is 41.

The spelling of 19651021961 in words is "nineteen billion, six hundred fifty-one million, twenty-one thousand, nine hundred sixty-one".