653721 has 4 divisors (see below), whose sum is σ = 871632. Its totient is φ = 435812.

The previous prime is 653713. The next prime is 653743. The reversal of 653721 is 127356.

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 a cyclic number.

It is not a de Polignac number, because 653721 - 2³ = 653713 is a prime.

It is a super-2 number, since 2×653721² = 854702291682, which contains 22 as substring.

It is a D-number.

It is a junction number, because it is equal to n+sod(n) for n = 653691 and 653700.

It is not an unprimeable number, because it can be changed into a prime (653711) 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, 108951 + ... + 108956.

It is an arithmetic number, because the mean of its divisors is an integer number (217908).

2⁶⁵³⁷²¹ is an apocalyptic number.

It is an amenable number.

653721 is a deficient number, since it is larger than the sum of its proper divisors (217911).

653721 is a wasteful number, since it uses less digits than its factorization.

653721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217910.

The product of its digits is 1260, while the sum is 24.

The square root of 653721 is about 808.5301478609. The cubic root of 653721 is about 86.7888923047.

The spelling of 653721 in words is "six hundred fifty-three thousand, seven hundred twenty-one".