102721661 has 4 divisors (see below), whose sum is σ = 117396192. Its totient is φ = 88047132.

The previous prime is 102721637. The next prime is 102721669. The reversal of 102721661 is 166127201.

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, and also an emirpimes, since its reverse is a distinct semiprime: 166127201 = 2063 ⋅80527.

It is a cyclic number.

It is not a de Polignac number, because 102721661 - 2¹⁴ = 102705277 is a prime.

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 102721661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (102721669) 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, 7337255 + ... + 7337268.

It is an arithmetic number, because the mean of its divisors is an integer number (29349048).

Almost surely, 2^102721661 is an apocalyptic number.

It is an amenable number.

102721661 is a deficient number, since it is larger than the sum of its proper divisors (14674531).

102721661 is an equidigital number, since it uses as much as digits as its factorization.

102721661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14674530.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 102721661 is about 10135.1695101759. The cubic root of 102721661 is about 468.3321919513.

Adding to 102721661 its reverse (166127201), we get a palindrome (268848862).

The spelling of 102721661 in words is "one hundred two million, seven hundred twenty-one thousand, six hundred sixty-one".