661611731 has 4 divisors (see below), whose sum is σ = 721758264. Its totient is φ = 601465200.

The previous prime is 661611677. The next prime is 661611733. The reversal of 661611731 is 137116166.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661611731 is a prime.

It is a super-2 number, since 2×661611731² = 875460165193632722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661611733) 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, 30073250 + ... + 30073271.

It is an arithmetic number, because the mean of its divisors is an integer number (180439566).

Almost surely, 2^661611731 is an apocalyptic number.

661611731 is a deficient number, since it is larger than the sum of its proper divisors (60146533).

661611731 is a wasteful number, since it uses less digits than its factorization.

661611731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60146532.

The product of its digits is 4536, while the sum is 32.

The square root of 661611731 is about 25721.8143022610. The cubic root of 661611731 is about 871.3669140709.

Adding to 661611731 its reverse (137116166), we get a palindrome (798727897).

The spelling of 661611731 in words is "six hundred sixty-one million, six hundred eleven thousand, seven hundred thirty-one".