216861631 has 4 divisors (see below), whose sum is σ = 247841872. Its totient is φ = 185881392.

The previous prime is 216861629. The next prime is 216861661. The reversal of 216861631 is 136168612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 216861631 - 2¹ = 216861629 is a prime.

It is a super-2 number, since 2×216861631² = 94057933999960322, 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 (216861661) 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, 15490110 + ... + 15490123.

It is an arithmetic number, because the mean of its divisors is an integer number (61960468).

Almost surely, 2^216861631 is an apocalyptic number.

216861631 is a deficient number, since it is larger than the sum of its proper divisors (30980241).

216861631 is an equidigital number, since it uses as much as digits as its factorization.

216861631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30980240.

The product of its digits is 10368, while the sum is 34.

The square root of 216861631 is about 14726.2225638485. Note that the first 3 decimals coincide. The cubic root of 216861631 is about 600.7967480009.

The spelling of 216861631 in words is "two hundred sixteen million, eight hundred sixty-one thousand, six hundred thirty-one".