840157921 has 4 divisors (see below), whose sum is σ = 842318100. Its totient is φ = 837997744.

The previous prime is 840157891. The next prime is 840157931. The reversal of 840157921 is 129751048.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 103306896 + 736851025 = 10164^2 + 27145^2 .

It is a cyclic number.

It is not a de Polignac number, because 840157921 - 2⁷ = 840157793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (840157931) 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, 1079506 + ... + 1080283.

It is an arithmetic number, because the mean of its divisors is an integer number (210579525).

Almost surely, 2^840157921 is an apocalyptic number.

It is an amenable number.

840157921 is a deficient number, since it is larger than the sum of its proper divisors (2160179).

840157921 is a wasteful number, since it uses less digits than its factorization.

840157921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2160178.

The product of its (nonzero) digits is 20160, while the sum is 37.

The square root of 840157921 is about 28985.4777604234. The cubic root of 840157921 is about 943.5979211639.

The spelling of 840157921 in words is "eight hundred forty million, one hundred fifty-seven thousand, nine hundred twenty-one".