661638013401 has 4 divisors (see below), whose sum is σ = 882184017872. Its totient is φ = 441092008932.

The previous prime is 661638013391. The next prime is 661638013447. The reversal of 661638013401 is 104310836166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 661638013401 - 2¹⁴ = 661637997017 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 661638013401.

It is not an unprimeable number, because it can be changed into a prime (661638013801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110273002231 + ... + 110273002236.

It is an arithmetic number, because the mean of its divisors is an integer number (220546004468).

Almost surely, 2^661638013401 is an apocalyptic number.

It is an amenable number.

661638013401 is a deficient number, since it is larger than the sum of its proper divisors (220546004471).

661638013401 is a wasteful number, since it uses less digits than its factorization.

661638013401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220546004470.

The product of its (nonzero) digits is 62208, while the sum is 39.

Adding to 661638013401 its reverse (104310836166), we get a palindrome (765948849567).

The spelling of 661638013401 in words is "six hundred sixty-one billion, six hundred thirty-eight million, thirteen thousand, four hundred one".