102139721 has 6 divisors (see below), whose sum is σ = 104976270. Its totient is φ = 99377856.

The previous prime is 102139633. The next prime is 102139729. The reversal of 102139721 is 127931201.

It can be written as a sum of positive squares in 3 ways, for example, as 85008400 + 17131321 = 9220^2 + 4139^2 .

It is not a de Polignac number, because 102139721 - 2¹⁴ = 102123337 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (102139729) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35936 + ... + 38673.

It is an arithmetic number, because the mean of its divisors is an integer number (17496045).

Almost surely, 2^102139721 is an apocalyptic number.

It is an amenable number.

102139721 is a deficient number, since it is larger than the sum of its proper divisors (2836549).

102139721 is an frugal number, since it uses more digits than its factorization.

102139721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74683 (or 74646 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 26.

The square root of 102139721 is about 10106.4197913999. The cubic root of 102139721 is about 467.4461161647.

The spelling of 102139721 in words is "one hundred two million, one hundred thirty-nine thousand, seven hundred twenty-one".