30721721 has 8 divisors (see below), whose sum is σ = 32124480. Its totient is φ = 29324592.

The previous prime is 30721709. The next prime is 30721723. The reversal of 30721721 is 12712703.

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 30721721 - 2⁶ = 30721657 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (30721723) 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, 13010 + ... + 15188.

It is an arithmetic number, because the mean of its divisors is an integer number (4015560).

Almost surely, 2^30721721 is an apocalyptic number.

It is an amenable number.

30721721 is a deficient number, since it is larger than the sum of its proper divisors (1402759).

30721721 is a wasteful number, since it uses less digits than its factorization.

30721721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2815.

The product of its (nonzero) digits is 588, while the sum is 23.

The square root of 30721721 is about 5542.7178351419. The cubic root of 30721721 is about 313.1952596975.

The spelling of 30721721 in words is "thirty million, seven hundred twenty-one thousand, seven hundred twenty-one".