1642688261 has 4 divisors (see below), whose sum is σ = 1646911500. Its totient is φ = 1638465024.

The previous prime is 1642688237. The next prime is 1642688273. The reversal of 1642688261 is 1628862461.

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: 1628862461 = 23 ⋅70820107.

It can be written as a sum of positive squares in 2 ways, for example, as 518427361 + 1124260900 = 22769^2 + 33530^2 .

It is a cyclic number.

It is not a de Polignac number, because 1642688261 - 2²² = 1638493957 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 (1642684261) 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, 2111036 + ... + 2111813.

It is an arithmetic number, because the mean of its divisors is an integer number (411727875).

Almost surely, 2^1642688261 is an apocalyptic number.

It is an amenable number.

1642688261 is a deficient number, since it is larger than the sum of its proper divisors (4223239).

1642688261 is an equidigital number, since it uses as much as digits as its factorization.

1642688261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4223238.

The product of its digits is 221184, while the sum is 44.

The square root of 1642688261 is about 40530.0908091753. The cubic root of 1642688261 is about 1179.9177049282.

The spelling of 1642688261 in words is "one billion, six hundred forty-two million, six hundred eighty-eight thousand, two hundred sixty-one".