16535515981 has 8 divisors (see below), whose sum is σ = 16591493880. Its totient is φ = 16479579648.

The previous prime is 16535515979. The next prime is 16535516071. The reversal of 16535515981 is 18951553561.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 102839881 + 16432676100 = 10141^2 + 128190^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 16535515981 - 2¹ = 16535515979 is a prime.

It is a super-2 number, since 2×16535515981² (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 (16535515921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 927015 + ... + 944683.

It is an arithmetic number, because the mean of its divisors is an integer number (2073936735).

Almost surely, 2^16535515981 is an apocalyptic number.

It is an amenable number.

16535515981 is a deficient number, since it is larger than the sum of its proper divisors (55977899).

16535515981 is a wasteful number, since it uses less digits than its factorization.

16535515981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20783.

The product of its digits is 810000, while the sum is 49.

The spelling of 16535515981 in words is "sixteen billion, five hundred thirty-five million, five hundred fifteen thousand, nine hundred eighty-one".