840307721 has 16 divisors (see below), whose sum is σ = 926830080. Its totient is φ = 755518080.

The previous prime is 840307717. The next prime is 840307723. The reversal of 840307721 is 127703048.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 840307721 - 2² = 840307717 is a prime.

It is a super-2 number, since 2×840307721² = 1412234131944427682, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (840307723) 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, 476840 + ... + 478598.

It is an arithmetic number, because the mean of its divisors is an integer number (57926880).

Almost surely, 2^840307721 is an apocalyptic number.

It is an amenable number.

840307721 is a deficient number, since it is larger than the sum of its proper divisors (86522359).

840307721 is a wasteful number, since it uses less digits than its factorization.

840307721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2224.

The product of its (nonzero) digits is 9408, while the sum is 32.

The square root of 840307721 is about 28988.0616978783. The cubic root of 840307721 is about 943.6539989420.

The spelling of 840307721 in words is "eight hundred forty million, three hundred seven thousand, seven hundred twenty-one".