20603561 has 32 divisors (see below), whose sum is σ = 25214976. Its totient is φ = 16632000.

The previous prime is 20603533. The next prime is 20603563. The reversal of 20603561 is 16530602.

It is not a de Polignac number, because 20603561 - 2¹⁸ = 20341417 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20603563) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 290156 + ... + 290226.

It is an arithmetic number, because the mean of its divisors is an integer number (787968).

Almost surely, 2^20603561 is an apocalyptic number.

It is an amenable number.

20603561 is a deficient number, since it is larger than the sum of its proper divisors (4611415).

20603561 is a wasteful number, since it uses less digits than its factorization.

20603561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173.

The product of its (nonzero) digits is 1080, while the sum is 23.

The square root of 20603561 is about 4539.1145612333. The cubic root of 20603561 is about 274.1452734524.

The spelling of 20603561 in words is "twenty million, six hundred three thousand, five hundred sixty-one".