2157664661 has 4 divisors (see below), whose sum is σ = 2251476192. Its totient is φ = 2063853132.

The previous prime is 2157664627. The next prime is 2157664727. The reversal of 2157664661 is 1664667512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2157664661 - 2¹⁴ = 2157648277 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 (2157664261) 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, 46905731 + ... + 46905776.

It is an arithmetic number, because the mean of its divisors is an integer number (562869048).

Almost surely, 2^2157664661 is an apocalyptic number.

It is an amenable number.

2157664661 is a deficient number, since it is larger than the sum of its proper divisors (93811531).

2157664661 is an equidigital number, since it uses as much as digits as its factorization.

2157664661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93811530.

The product of its digits is 362880, while the sum is 44.

The square root of 2157664661 is about 46450.6691125112. The cubic root of 2157664661 is about 1292.1947816398.

The spelling of 2157664661 in words is "two billion, one hundred fifty-seven million, six hundred sixty-four thousand, six hundred sixty-one".