20623521 has 4 divisors (see below), whose sum is σ = 27498032. Its totient is φ = 13749012.

The previous prime is 20623513. The next prime is 20623573. The reversal of 20623521 is 12532602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20623521 - 2³ = 20623513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20623121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3437251 + ... + 3437256.

It is an arithmetic number, because the mean of its divisors is an integer number (6874508).

Almost surely, 2^20623521 is an apocalyptic number.

It is an amenable number.

20623521 is a deficient number, since it is larger than the sum of its proper divisors (6874511).

20623521 is an equidigital number, since it uses as much as digits as its factorization.

20623521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6874510.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 20623521 is about 4541.3126956861. The cubic root of 20623521 is about 274.2337722901.

The spelling of 20623521 in words is "twenty million, six hundred twenty-three thousand, five hundred twenty-one".