11721503661 has 16 divisors (see below), whose sum is σ = 17863077888. Its totient is φ = 6697350000.

The previous prime is 11721503659. The next prime is 11721503669. The reversal of 11721503661 is 16630512711.

It is not a de Polignac number, because 11721503661 - 2¹ = 11721503659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11721503669) 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, 268476 + ... + 309066.

It is an arithmetic number, because the mean of its divisors is an integer number (1116442368).

Almost surely, 2^11721503661 is an apocalyptic number.

It is an amenable number.

11721503661 is a deficient number, since it is larger than the sum of its proper divisors (6141574227).

11721503661 is a wasteful number, since it uses less digits than its factorization.

11721503661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54352.

The product of its (nonzero) digits is 7560, while the sum is 33.

It can be divided in two parts, 1172150 and 3661, that added together give a triangular number (1175811 = T₁₅₃₃).

The spelling of 11721503661 in words is "eleven billion, seven hundred twenty-one million, five hundred three thousand, six hundred sixty-one".