20661538239967 has 6 divisors (see below), whose sum is σ = 21948416054528. Its totient is φ = 19446153637344.

The previous prime is 20661538239961. The next prime is 20661538240033. The reversal of 20661538239967 is 76993283516602.

It is a de Polignac number, because none of the positive numbers 2^k-20661538239967 is a prime.

It is a super-3 number, since 3×20661538239967³ (a number of 41 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20661538239961) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35746605663 + ... + 35746606240.

Almost surely, 2^{20661538239967} is an apocalyptic number.

20661538239967 is a deficient number, since it is larger than the sum of its proper divisors (1286877814561).

20661538239967 is an equidigital number, since it uses as much as digits as its factorization.

20661538239967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71493211937 (or 71493211920 counting only the distinct ones).

The product of its (nonzero) digits is 176359680, while the sum is 67.

The spelling of 20661538239967 in words is "twenty trillion, six hundred sixty-one billion, five hundred thirty-eight million, two hundred thirty-nine thousand, nine hundred sixty-seven".