168699721 has 8 divisors (see below), whose sum is σ = 178872840. Its totient is φ = 158554368.

The previous prime is 168699701. The next prime is 168699749. The reversal of 168699721 is 127996861.

It can be written as a sum of positive squares in 4 ways, for example, as 44689225 + 124010496 = 6685^2 + 11136^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 168699721 - 2¹³ = 168691529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (168699701) 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, 6315 + ... + 19423.

It is an arithmetic number, because the mean of its divisors is an integer number (22359105).

Almost surely, 2^168699721 is an apocalyptic number.

It is an amenable number.

168699721 is a deficient number, since it is larger than the sum of its proper divisors (10173119).

168699721 is a wasteful number, since it uses less digits than its factorization.

168699721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13883.

The product of its digits is 326592, while the sum is 49.

The square root of 168699721 is about 12988.4456729818. The cubic root of 168699721 is about 552.5498365534.

The spelling of 168699721 in words is "one hundred sixty-eight million, six hundred ninety-nine thousand, seven hundred twenty-one".