30721920 has 64 divisors (see below), whose sum is σ = 97932240. Its totient is φ = 8192000.

The previous prime is 30721871. The next prime is 30721939. The reversal of 30721920 is 2912703.

It is a tau number, because it is divible by the number of its divisors (64).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6081 + ... + 9920.

Almost surely, 2^30721920 is an apocalyptic number.

30721920 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

30721920 is an abundant number, since it is smaller than the sum of its proper divisors (67210320).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

30721920 is a wasteful number, since it uses less digits than its factorization.

30721920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16023 (or 16011 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 24.

The square root of 30721920 is about 5542.7357865949. The cubic root of 30721920 is about 313.1959359370.

The spelling of 30721920 in words is "thirty million, seven hundred twenty-one thousand, nine hundred twenty".