30720721 has 8 divisors (see below), whose sum is σ = 31797504. Its totient is φ = 29649360.

The previous prime is 30720719. The next prime is 30720733. The reversal of 30720721 is 12702703.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 30720721 - 2¹ = 30720719 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 30720692 and 30720701.

It is not an unprimeable number, because it can be changed into a prime (30720421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12615 + ... + 14851.

It is an arithmetic number, because the mean of its divisors is an integer number (3974688).

Almost surely, 2^30720721 is an apocalyptic number.

30720721 is a gapful number since it is divisible by the number (31) formed by its first and last digit.

It is an amenable number.

30720721 is a deficient number, since it is larger than the sum of its proper divisors (1076783).

30720721 is a wasteful number, since it uses less digits than its factorization.

30720721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2711.

The product of its (nonzero) digits is 588, while the sum is 22.

The square root of 30720721 is about 5542.6276259550. The cubic root of 30720721 is about 313.1918614649.

The spelling of 30720721 in words is "thirty million, seven hundred twenty thousand, seven hundred twenty-one".