1543690661 has 8 divisors (see below), whose sum is σ = 1636922520. Its totient is φ = 1450728448.

The previous prime is 1543690639. The next prime is 1543690679. The reversal of 1543690661 is 1660963451.

It can be written as a sum of positive squares in 4 ways, for example, as 903904225 + 639786436 = 30065^2 + 25294^2 .

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 1543690661 - 2²⁶ = 1476581797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1543690261) 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, 55556 + ... + 78573.

It is an arithmetic number, because the mean of its divisors is an integer number (204615315).

Almost surely, 2^1543690661 is an apocalyptic number.

It is an amenable number.

1543690661 is a deficient number, since it is larger than the sum of its proper divisors (93231859).

1543690661 is a wasteful number, since it uses less digits than its factorization.

1543690661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134823.

The product of its (nonzero) digits is 116640, while the sum is 41.

The square root of 1543690661 is about 39289.8289764667. The cubic root of 1543690661 is about 1155.7221200936.

The spelling of 1543690661 in words is "one billion, five hundred forty-three million, six hundred ninety thousand, six hundred sixty-one".