161021551 has 8 divisors (see below), whose sum is σ = 168682464. Its totient is φ = 153415680.

The previous prime is 161021519. The next prime is 161021591. The reversal of 161021551 is 155120161.

It is a happy number.

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 161021551 - 2⁵ = 161021519 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161021591) 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, 7710 + ... + 19531.

It is an arithmetic number, because the mean of its divisors is an integer number (21085308).

Almost surely, 2^161021551 is an apocalyptic number.

161021551 is a deficient number, since it is larger than the sum of its proper divisors (7660913).

161021551 is a wasteful number, since it uses less digits than its factorization.

161021551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27521.

The product of its (nonzero) digits is 300, while the sum is 22.

The square root of 161021551 is about 12689.4267404008. The cubic root of 161021551 is about 544.0364547640.

The spelling of 161021551 in words is "one hundred sixty-one million, twenty-one thousand, five hundred fifty-one".