661672729 has 9 divisors (see below), whose sum is σ = 686049247. Its totient is φ = 638136184.

The previous prime is 661672727. The next prime is 661672751. The reversal of 661672729 is 927276166.

The square root of 661672729 is 25723.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 346965129 + 314707600 = 18627^2 + 17740^2 .

It is not a de Polignac number, because 661672729 - 2¹ = 661672727 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661672727) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 745524 + ... + 746410.

Almost surely, 2^661672729 is an apocalyptic number.

661672729 is the 25723-rd square number.

661672729 is the 12862-nd centered octagonal number.

It is an amenable number.

661672729 is a deficient number, since it is larger than the sum of its proper divisors (24376518).

661672729 is an frugal number, since it uses more digits than its factorization.

661672729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1832 (or 916 counting only the distinct ones).

The product of its digits is 381024, while the sum is 46.

The cubic root of 661672729 is about 871.3936921157.

The spelling of 661672729 in words is "six hundred sixty-one million, six hundred seventy-two thousand, seven hundred twenty-nine".