7421721 has 4 divisors (see below), whose sum is σ = 9895632. Its totient is φ = 4947812.

The previous prime is 7421717. The next prime is 7421759. The reversal of 7421721 is 1271247.

7421721 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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: 1271247 = 3 ⋅423749.

It is a cyclic number.

It is not a de Polignac number, because 7421721 - 2² = 7421717 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 7421691 and 7421700.

It is not an unprimeable number, because it can be changed into a prime (7421021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1236951 + ... + 1236956.

It is an arithmetic number, because the mean of its divisors is an integer number (2473908).

Almost surely, 2^7421721 is an apocalyptic number.

It is an amenable number.

7421721 is a deficient number, since it is larger than the sum of its proper divisors (2473911).

7421721 is a wasteful number, since it uses less digits than its factorization.

7421721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2473910.

The product of its digits is 784, while the sum is 24.

The square root of 7421721 is about 2724.2835755479. The cubic root of 7421721 is about 195.0599946891.

Adding to 7421721 its reverse (1271247), we get a palindrome (8692968).

The spelling of 7421721 in words is "seven million, four hundred twenty-one thousand, seven hundred twenty-one".