656666661 has 16 divisors (see below), whose sum is σ = 1019516544. Its totient is φ = 368157504.

The previous prime is 656666603. The next prime is 656666669. The reversal of 656666661 is 166666656.

It is not a de Polignac number, because 656666661 - 2¹⁰ = 656665637 is a prime.

It is a super-2 number, since 2×656666661² = 862422207337777842, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 656666661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (656666669) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 293886 + ... + 296111.

It is an arithmetic number, because the mean of its divisors is an integer number (63719784).

Almost surely, 2^656666661 is an apocalyptic number.

It is an amenable number.

656666661 is a deficient number, since it is larger than the sum of its proper divisors (362849883).

656666661 is a wasteful number, since it uses less digits than its factorization.

656666661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 590060.

The product of its digits is 1399680, while the sum is 48.

The square root of 656666661 is about 25625.5080144765. The cubic root of 656666661 is about 869.1905365646.

It can be divided in two parts, 65666 and 6661, that added together give a palindrome (72327).

The spelling of 656666661 in words is "six hundred fifty-six million, six hundred sixty-six thousand, six hundred sixty-one".