20749632561 has 36 divisors (see below), whose sum is σ = 35014837572. Its totient is φ = 11805986304.

The previous prime is 20749632539. The next prime is 20749632593. The reversal of 20749632561 is 16523694702.

20749632561 is a `hidden beast` number, since 2 + 0 + 7 + 4 + 9 + 632 + 5 + 6 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10757630961 + 9992001600 = 103719^2 + 99960^2 .

It is not a de Polignac number, because 20749632561 - 2⁷ = 20749632433 is a prime.

It is a super-2 number, since 2×20749632561² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20749632511) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1785 + ... + 203721.

It is an arithmetic number, because the mean of its divisors is an integer number (972634377).

Almost surely, 2^20749632561 is an apocalyptic number.

20749632561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20749632561 is a deficient number, since it is larger than the sum of its proper divisors (14265205011).

20749632561 is a wasteful number, since it uses less digits than its factorization.

20749632561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202190 (or 202180 counting only the distinct ones).

The product of its (nonzero) digits is 544320, while the sum is 45.

The spelling of 20749632561 in words is "twenty billion, seven hundred forty-nine million, six hundred thirty-two thousand, five hundred sixty-one".