216402661 has 4 divisors (see below), whose sum is σ = 223383424. Its totient is φ = 209421900.

The previous prime is 216402643. The next prime is 216402679. The reversal of 216402661 is 166204612.

216402661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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.

It is an interprime number because it is at equal distance from previous prime (216402643) and next prime (216402679).

It is a cyclic number.

It is not a de Polignac number, because 216402661 - 2⁵ = 216402629 is a prime.

It is a super-2 number, since 2×216402661² = 93660223375761842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216406661) 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, 3490335 + ... + 3490396.

It is an arithmetic number, because the mean of its divisors is an integer number (55845856).

Almost surely, 2^216402661 is an apocalyptic number.

It is an amenable number.

216402661 is a deficient number, since it is larger than the sum of its proper divisors (6980763).

216402661 is an equidigital number, since it uses as much as digits as its factorization.

216402661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6980762.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 216402661 is about 14710.6308838200. The cubic root of 216402661 is about 600.3726028233.

The spelling of 216402661 in words is "two hundred sixteen million, four hundred two thousand, six hundred sixty-one".