20521749 has 4 divisors (see below), whose sum is σ = 27362336. Its totient is φ = 13681164.

The previous prime is 20521747. The next prime is 20521777. The reversal of 20521749 is 94712502.

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 20521749 - 2¹ = 20521747 is a prime.

It is a super-2 number, since 2×20521749² = 842284364038002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521747) 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, 3420289 + ... + 3420294.

It is an arithmetic number, because the mean of its divisors is an integer number (6840584).

Almost surely, 2^20521749 is an apocalyptic number.

It is an amenable number.

20521749 is a deficient number, since it is larger than the sum of its proper divisors (6840587).

20521749 is an equidigital number, since it uses as much as digits as its factorization.

20521749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6840586.

The product of its (nonzero) digits is 5040, while the sum is 30.

The square root of 20521749 is about 4530.0937076401. The cubic root of 20521749 is about 273.7819361836.

The spelling of 20521749 in words is "twenty million, five hundred twenty-one thousand, seven hundred forty-nine".