213043661 has 8 divisors (see below), whose sum is σ = 217423800. Its totient is φ = 208707840.

The previous prime is 213043651. The next prime is 213043693. The reversal of 213043661 is 166340312.

It can be written as a sum of positive squares in 4 ways, for example, as 45832900 + 167210761 = 6770^2 + 12931^2 .

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 213043661 - 2²² = 208849357 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 213043661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (213043651) 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, 1280 + ... + 20681.

It is an arithmetic number, because the mean of its divisors is an integer number (27177975).

Almost surely, 2^213043661 is an apocalyptic number.

It is an amenable number.

213043661 is a deficient number, since it is larger than the sum of its proper divisors (4380139).

213043661 is a wasteful number, since it uses less digits than its factorization.

213043661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22159.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 213043661 is about 14596.0152438945. The cubic root of 213043661 is about 597.2500647560.

Adding to 213043661 its reverse (166340312), we get a palindrome (379383973).

The spelling of 213043661 in words is "two hundred thirteen million, forty-three thousand, six hundred sixty-one".