840000721 has 4 divisors (see below), whose sum is σ = 960000832. Its totient is φ = 720000612.

The previous prime is 840000703. The next prime is 840000727. The reversal of 840000721 is 127000048.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 840000721 - 2⁷ = 840000593 is a prime.

It is a super-2 number, since 2×840000721² = 1411202422561039682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 840000692 and 840000701.

It is not an unprimeable number, because it can be changed into a prime (840000727) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60000045 + ... + 60000058.

It is an arithmetic number, because the mean of its divisors is an integer number (240000208).

Almost surely, 2^840000721 is an apocalyptic number.

It is an amenable number.

840000721 is a deficient number, since it is larger than the sum of its proper divisors (120000111).

840000721 is a wasteful number, since it uses less digits than its factorization.

840000721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 120000110.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 840000721 is about 28982.7659308079. The cubic root of 840000721 is about 943.5390660202.

Adding to 840000721 its reverse (127000048), we get a palindrome (967000769).

The spelling of 840000721 in words is "eight hundred forty million, seven hundred twenty-one", and thus it is an aban number.