7720421 has 4 divisors (see below), whose sum is σ = 7729344. Its totient is φ = 7711500.

The previous prime is 7720399. The next prime is 7720429. The reversal of 7720421 is 1240277.

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: 1240277 = 37 ⋅33521.

It is a cyclic number.

It is not a de Polignac number, because 7720421 - 2⁶ = 7720357 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 (7720429) 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, 3005 + ... + 4946.

It is an arithmetic number, because the mean of its divisors is an integer number (1932336).

Almost surely, 2^7720421 is an apocalyptic number.

It is an amenable number.

7720421 is a deficient number, since it is larger than the sum of its proper divisors (8923).

7720421 is an equidigital number, since it uses as much as digits as its factorization.

7720421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8922.

The product of its (nonzero) digits is 784, while the sum is 23.

The square root of 7720421 is about 2778.5645574649. The cubic root of 7720421 is about 197.6424950402.

Adding to 7720421 its reverse (1240277), we get a palindrome (8960698).

The spelling of 7720421 in words is "seven million, seven hundred twenty thousand, four hundred twenty-one".