20621563 has 4 divisors (see below), whose sum is σ = 20630808. Its totient is φ = 20612320.

The previous prime is 20621537. The next prime is 20621569. The reversal of 20621563 is 36512602.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20621563 - 2¹³ = 20613371 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20621569) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1020 + ... + 6502.

It is an arithmetic number, because the mean of its divisors is an integer number (5157702).

Almost surely, 2^20621563 is an apocalyptic number.

20621563 is a deficient number, since it is larger than the sum of its proper divisors (9245).

20621563 is an equidigital number, since it uses as much as digits as its factorization.

20621563 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9244.

The product of its (nonzero) digits is 2160, while the sum is 25.

The square root of 20621563 is about 4541.0971141344. The cubic root of 20621563 is about 274.2250934177.

The spelling of 20621563 in words is "twenty million, six hundred twenty-one thousand, five hundred sixty-three".