2066639131561 has 3 divisors (see below), whose sum is σ = 2066640569143. Its totient is φ = 2066637693980.

The previous prime is 2066639131507. The next prime is 2066639131567. The reversal of 2066639131561 is 1651319366602.

The square root of 2066639131561 is 1437581.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 726277223961 + 1340361907600 = 852219^2 + 1157740^2 .

It is not a de Polignac number, because 2066639131561 - 2¹⁹ = 2066638607273 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2066639131567) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 718791 + ... + 2156371.

Almost surely, 2^{2066639131561} is an apocalyptic number.

2066639131561 is the 1437581-st square number.

2066639131561 is the 718791-st centered octagonal number.

It is an amenable number.

2066639131561 is a deficient number, since it is larger than the sum of its proper divisors (1437582).

2066639131561 is an frugal number, since it uses more digits than its factorization.

2066639131561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2875162 (or 1437581 counting only the distinct ones).

The product of its (nonzero) digits is 1049760, while the sum is 49.

Multiplying 2066639131561 by its sum of digits (49), we get a square (101265317446489 = 10063067²).

The spelling of 2066639131561 in words is "two trillion, sixty-six billion, six hundred thirty-nine million, one hundred thirty-one thousand, five hundred sixty-one".