720221821 has 4 divisors (see below), whose sum is σ = 785696544. Its totient is φ = 654747100.

The previous prime is 720221819. The next prime is 720221861. The reversal of 720221821 is 128122027.

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: 128122027 = 11 ⋅11647457.

It is a cyclic number.

It is not a de Polignac number, because 720221821 - 2¹ = 720221819 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 (720221861) 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, 32737345 + ... + 32737366.

It is an arithmetic number, because the mean of its divisors is an integer number (196424136).

Almost surely, 2^720221821 is an apocalyptic number.

It is an amenable number.

720221821 is a deficient number, since it is larger than the sum of its proper divisors (65474723).

720221821 is a wasteful number, since it uses less digits than its factorization.

720221821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65474722.

The product of its (nonzero) digits is 896, while the sum is 25.

The square root of 720221821 is about 26836.9488019782. The cubic root of 720221821 is about 896.3729833498.

Adding to 720221821 its reverse (128122027), we get a palindrome (848343848).

The spelling of 720221821 in words is "seven hundred twenty million, two hundred twenty-one thousand, eight hundred twenty-one".