21519168961 has 4 divisors (see below), whose sum is σ = 22261209300. Its totient is φ = 20777128624.

The previous prime is 21519168917. The next prime is 21519169027. The reversal of 21519168961 is 16986191512.

It is a happy number.

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 17205306561 + 4313862400 = 131169^2 + 65680^2 .

It is a cyclic number.

It is not a de Polignac number, because 21519168961 - 2¹³ = 21519160769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21519168901) 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, 371020126 + ... + 371020183.

It is an arithmetic number, because the mean of its divisors is an integer number (5565302325).

Almost surely, 2^21519168961 is an apocalyptic number.

It is an amenable number.

21519168961 is a deficient number, since it is larger than the sum of its proper divisors (742040339).

21519168961 is an equidigital number, since it uses as much as digits as its factorization.

21519168961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 742040338.

The product of its digits is 233280, while the sum is 49.

The spelling of 21519168961 in words is "twenty-one billion, five hundred nineteen million, one hundred sixty-eight thousand, nine hundred sixty-one".