30721640 has 16 divisors (see below), whose sum is σ = 69123780. Its totient is φ = 12288640.

The previous prime is 30721637. The next prime is 30721657. The reversal of 30721640 is 4612703.

It can be written as a sum of positive squares in 2 ways, for example, as 25180324 + 5541316 = 5018^2 + 2354^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 383981 + ... + 384060.

Almost surely, 2^30721640 is an apocalyptic number.

It is an amenable number.

30721640 is an abundant number, since it is smaller than the sum of its proper divisors (38402140).

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

30721640 is a wasteful number, since it uses less digits than its factorization.

30721640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 768052 (or 768048 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 23.

The square root of 30721640 is about 5542.7105282524. The cubic root of 30721640 is about 313.1949844434.

The spelling of 30721640 in words is "thirty million, seven hundred twenty-one thousand, six hundred forty".