2157697649 has 4 divisors (see below), whose sum is σ = 2160642036. Its totient is φ = 2154753264.

The previous prime is 2157697637. The next prime is 2157697657. The reversal of 2157697649 is 9467967512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1941019249 + 216678400 = 44057^2 + 14720^2 .

It is a cyclic number.

It is not a de Polignac number, because 2157697649 - 2¹² = 2157693553 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 2157697594 and 2157697603.

It is not an unprimeable number, because it can be changed into a prime (2157697249) 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, 1471094 + ... + 1472559.

It is an arithmetic number, because the mean of its divisors is an integer number (540160509).

Almost surely, 2^2157697649 is an apocalyptic number.

It is an amenable number.

2157697649 is a deficient number, since it is larger than the sum of its proper divisors (2944387).

2157697649 is an equidigital number, since it uses as much as digits as its factorization.

2157697649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2944386.

The product of its digits is 5715360, while the sum is 56.

The square root of 2157697649 is about 46451.0241975352. The cubic root of 2157697649 is about 1292.2013669548.

The spelling of 2157697649 in words is "two billion, one hundred fifty-seven million, six hundred ninety-seven thousand, six hundred forty-nine".