840357921 has 8 divisors (see below), whose sum is σ = 1206667840. Its totient is φ = 517143312.

The previous prime is 840357913. The next prime is 840357937. The reversal of 840357921 is 129753048.

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

It is not a de Polignac number, because 840357921 - 2³ = 840357913 is a prime.

It is a super-4 number, since 4×840357921⁴ (a number of 37 digits) contains 4444 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 21547639 = 840357921 / (8 + 4 + 0 + 3 + 5 + 7 + 9 + 2 + 1).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 840357921.

It is not an unprimeable number, because it can be changed into a prime (840357971) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10773781 + ... + 10773858.

It is an arithmetic number, because the mean of its divisors is an integer number (150833480).

Almost surely, 2^840357921 is an apocalyptic number.

It is an amenable number.

840357921 is a deficient number, since it is larger than the sum of its proper divisors (366309919).

840357921 is a wasteful number, since it uses less digits than its factorization.

840357921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21547655.

The product of its (nonzero) digits is 60480, while the sum is 39.

The square root of 840357921 is about 28988.9275586387. The cubic root of 840357921 is about 943.6727898708.

The spelling of 840357921 in words is "eight hundred forty million, three hundred fifty-seven thousand, nine hundred twenty-one".