20561651 has 12 divisors (see below), whose sum is σ = 22822800. Its totient is φ = 18509040.

The previous prime is 20561647. The next prime is 20561663. The reversal of 20561651 is 15616502.

It is not a de Polignac number, because 20561651 - 2² = 20561647 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20561651.

It is not an unprimeable number, because it can be changed into a prime (20561621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12410 + ... + 13968.

It is an arithmetic number, because the mean of its divisors is an integer number (1901900).

Almost surely, 2^20561651 is an apocalyptic number.

20561651 is a deficient number, since it is larger than the sum of its proper divisors (2261149).

20561651 is a wasteful number, since it uses less digits than its factorization.

20561651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1690 (or 1679 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 20561651 is about 4534.4956720676. The cubic root of 20561651 is about 273.9592663265.

It can be divided in two parts, 20561 and 651, that added together give a palindrome (21212).

The spelling of 20561651 in words is "twenty million, five hundred sixty-one thousand, six hundred fifty-one".