216861645 has 144 divisors (see below), whose sum is σ = 476654976. Its totient is φ = 82368000.

The previous prime is 216861629. The next prime is 216861661. The reversal of 216861645 is 546168612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (216861629) and next prime (216861661).

It is not a de Polignac number, because 216861645 - 2⁴ = 216861629 is a prime.

It is a super-3 number, since 3×216861645³ (a number of 26 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 2147095 + ... + 2147195.

It is an arithmetic number, because the mean of its divisors is an integer number (3310104).

Almost surely, 2^216861645 is an apocalyptic number.

It is an amenable number.

216861645 is an abundant number, since it is smaller than the sum of its proper divisors (259793331).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

216861645 is a wasteful number, since it uses less digits than its factorization.

216861645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164 (or 140 counting only the distinct ones).

The product of its digits is 69120, while the sum is 39.

The square root of 216861645 is about 14726.2230391910. The cubic root of 216861645 is about 600.7967609295.

The spelling of 216861645 in words is "two hundred sixteen million, eight hundred sixty-one thousand, six hundred forty-five".