30721638 has 8 divisors (see below), whose sum is σ = 61443288. Its totient is φ = 10240544.

The previous prime is 30721637. The next prime is 30721657. The reversal of 30721638 is 83612703.

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

30721638 is an admirable number.

It is an alternating number because its digits alternate between odd and even.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (30721637) 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, 2560131 + ... + 2560142.

It is an arithmetic number, because the mean of its divisors is an integer number (7680411).

Almost surely, 2^30721638 is an apocalyptic number.

30721638 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

30721638 is a wasteful number, since it uses less digits than its factorization.

30721638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5120278.

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 30721638 is about 5542.7103478353. The cubic root of 30721638 is about 313.1949776470.

It can be divided in two parts, 307 and 21638, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 30721638 in words is "thirty million, seven hundred twenty-one thousand, six hundred thirty-eight".