381521721 has 16 divisors (see below), whose sum is σ = 582626304. Its totient is φ = 217539984.

The previous prime is 381521713. The next prime is 381521737. The reversal of 381521721 is 127125183.

It is not a de Polignac number, because 381521721 - 2³ = 381521713 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (381521711) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9645 + ... + 29258.

It is an arithmetic number, because the mean of its divisors is an integer number (36414144).

Almost surely, 2^381521721 is an apocalyptic number.

It is an amenable number.

381521721 is a deficient number, since it is larger than the sum of its proper divisors (201104583).

381521721 is a wasteful number, since it uses less digits than its factorization.

381521721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39380.

The product of its digits is 3360, while the sum is 30.

The square root of 381521721 is about 19532.5810122472. The cubic root of 381521721 is about 725.2812042729.

The spelling of 381521721 in words is "three hundred eighty-one million, five hundred twenty-one thousand, seven hundred twenty-one".