16641061981 has 4 divisors (see below), whose sum is σ = 17177870464. Its totient is φ = 16104253500.

The previous prime is 16641061979. The next prime is 16641062023. The reversal of 16641061981 is 18916014661.

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 16641061981 - 2¹ = 16641061979 is a prime.

It is a super-2 number, since 2×16641061981² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16641061681) 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, 268404195 + ... + 268404256.

It is an arithmetic number, because the mean of its divisors is an integer number (4294467616).

Almost surely, 2^16641061981 is an apocalyptic number.

It is an amenable number.

16641061981 is a deficient number, since it is larger than the sum of its proper divisors (536808483).

16641061981 is an equidigital number, since it uses as much as digits as its factorization.

16641061981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 536808482.

The product of its (nonzero) digits is 62208, while the sum is 43.

The spelling of 16641061981 in words is "sixteen billion, six hundred forty-one million, sixty-one thousand, nine hundred eighty-one".