720120821 has 4 divisors (see below), whose sum is σ = 822995232. Its totient is φ = 617246412.

The previous prime is 720120781. The next prime is 720120827. The reversal of 720120821 is 128021027.

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, and also an emirpimes, since its reverse is a distinct semiprime: 128021027 = 3023 ⋅42349.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-720120821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (720120827) 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, 51437195 + ... + 51437208.

It is an arithmetic number, because the mean of its divisors is an integer number (205748808).

Almost surely, 2^720120821 is an apocalyptic number.

It is an amenable number.

720120821 is a deficient number, since it is larger than the sum of its proper divisors (102874411).

720120821 is a wasteful number, since it uses less digits than its factorization.

720120821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102874410.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 720120821 is about 26835.0670019659. The cubic root of 720120821 is about 896.3310805632.

Adding to 720120821 its reverse (128021027), we get a palindrome (848141848).

The spelling of 720120821 in words is "seven hundred twenty million, one hundred twenty thousand, eight hundred twenty-one".