156405661 has 4 divisors (see below), whose sum is σ = 165606012. Its totient is φ = 147205312.

The previous prime is 156405653. The next prime is 156405713. The reversal of 156405661 is 166504651.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166504651 = 443 ⋅375857.

It can be written as a sum of positive squares in 2 ways, for example, as 122544900 + 33860761 = 11070^2 + 5819^2 .

It is not a de Polignac number, because 156405661 - 2³ = 156405653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (156405631) 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, 4600150 + ... + 4600183.

It is an arithmetic number, because the mean of its divisors is an integer number (41401503).

Almost surely, 2^156405661 is an apocalyptic number.

It is an amenable number.

156405661 is a deficient number, since it is larger than the sum of its proper divisors (9200351).

156405661 is an equidigital number, since it uses as much as digits as its factorization.

156405661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9200350.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 156405661 is about 12506.2248900298. The cubic root of 156405661 is about 538.7874725902.

The spelling of 156405661 in words is "one hundred fifty-six million, four hundred five thousand, six hundred sixty-one".