30628721 has 4 divisors (see below), whose sum is σ = 30739572. Its totient is φ = 30517872.

The previous prime is 30628657. The next prime is 30628723. The reversal of 30628721 is 12782603.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12782603 = 151 ⋅84653.

It can be written as a sum of positive squares in 2 ways, for example, as 14145121 + 16483600 = 3761^2 + 4060^2 .

It is a cyclic number.

It is not a de Polignac number, because 30628721 - 2⁶ = 30628657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (30628723) 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, 55010 + ... + 55563.

It is an arithmetic number, because the mean of its divisors is an integer number (7684893).

Almost surely, 2^30628721 is an apocalyptic number.

It is an amenable number.

30628721 is a deficient number, since it is larger than the sum of its proper divisors (110851).

30628721 is a wasteful number, since it uses less digits than its factorization.

30628721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110850.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 30628721 is about 5534.3220903739. The cubic root of 30628721 is about 312.8789080661.

The spelling of 30628721 in words is "thirty million, six hundred twenty-eight thousand, seven hundred twenty-one".