161321978906 has 32 divisors (see below), whose sum is σ = 267829246656. Its totient is φ = 72261072000.

The previous prime is 161321978903. The next prime is 161321978929. The reversal of 161321978906 is 609879123161.

161321978906 = T₂₅₆ + T₂₅₇ + ... + T₉₈₉₁.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (161321978903) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1837736 + ... + 1923516.

It is an arithmetic number, because the mean of its divisors is an integer number (8369663958).

Almost surely, 2^161321978906 is an apocalyptic number.

161321978906 is a deficient number, since it is larger than the sum of its proper divisors (106507267750).

161321978906 is a wasteful number, since it uses less digits than its factorization.

161321978906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87038.

The product of its (nonzero) digits is 979776, while the sum is 53.

The spelling of 161321978906 in words is "one hundred sixty-one billion, three hundred twenty-one million, nine hundred seventy-eight thousand, nine hundred six".