20561638 has 16 divisors (see below), whose sum is σ = 32060160. Its totient is φ = 9878400.

The previous prime is 20561633. The next prime is 20561647. The reversal of 20561638 is 83616502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20561633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13243 + ... + 14713.

It is an arithmetic number, because the mean of its divisors is an integer number (2003760).

Almost surely, 2^20561638 is an apocalyptic number.

20561638 is a deficient number, since it is larger than the sum of its proper divisors (11498522).

20561638 is a wasteful number, since it uses less digits than its factorization.

20561638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1743.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 20561638 is about 4534.4942386114. The cubic root of 20561638 is about 273.9592085900.

The spelling of 20561638 in words is "twenty million, five hundred sixty-one thousand, six hundred thirty-eight".