16561121517031 has 16 divisors (see below), whose sum is σ = 20383031905600. Its totient is φ = 13103232219648.

The previous prime is 16561121516981. The next prime is 16561121517041. The reversal of 16561121517031 is 13071512116561.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 16561121517031 - 2¹⁵ = 16561121484263 is a prime.

It is a super-2 number, since 2×16561121517031² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16561121517041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20976385 + ... + 21751573.

It is an arithmetic number, because the mean of its divisors is an integer number (1273939494100).

Almost surely, 2^{16561121517031} is an apocalyptic number.

16561121517031 is a deficient number, since it is larger than the sum of its proper divisors (3821910388569).

16561121517031 is a wasteful number, since it uses less digits than its factorization.

16561121517031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1009978.

The product of its (nonzero) digits is 37800, while the sum is 40.

The spelling of 16561121517031 in words is "sixteen trillion, five hundred sixty-one billion, one hundred twenty-one million, five hundred seventeen thousand, thirty-one".