53209721 has 4 divisors (see below), whose sum is σ = 54213732. Its totient is φ = 52205712.

The previous prime is 53209703. The next prime is 53209727. The reversal of 53209721 is 12790235.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12790235 = 5 ⋅2558047.

It can be written as a sum of positive squares in 2 ways, for example, as 12709225 + 40500496 = 3565^2 + 6364^2 .

It is a cyclic number.

It is not a de Polignac number, because 53209721 - 2⁶ = 53209657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (53209727) 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, 501926 + ... + 502031.

It is an arithmetic number, because the mean of its divisors is an integer number (13553433).

Almost surely, 2^53209721 is an apocalyptic number.

It is an amenable number.

53209721 is a deficient number, since it is larger than the sum of its proper divisors (1004011).

53209721 is a wasteful number, since it uses less digits than its factorization.

53209721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1004010.

The product of its (nonzero) digits is 3780, while the sum is 29.

The square root of 53209721 is about 7294.4993659606. The cubic root of 53209721 is about 376.1233774420.

Adding to 53209721 its reverse (12790235), we get a palindrome (65999956).

The spelling of 53209721 in words is "fifty-three million, two hundred nine thousand, seven hundred twenty-one".