18216649 has 16 divisors (see below), whose sum is σ = 21415680. Its totient is φ = 15316560.

The previous prime is 18216641. The next prime is 18216661. The reversal of 18216649 is 94661281.

18216649 = 185² + 186² + ... + 393².

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 18216649 - 2³ = 18216641 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18216641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7974 + ... + 10000.

It is an arithmetic number, because the mean of its divisors is an integer number (1338480).

Almost surely, 2^18216649 is an apocalyptic number.

18216649 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

18216649 is a deficient number, since it is larger than the sum of its proper divisors (3199031).

18216649 is a wasteful number, since it uses less digits than its factorization.

18216649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2100.

The product of its digits is 20736, while the sum is 37.

The square root of 18216649 is about 4268.0966483902. The cubic root of 18216649 is about 263.1213952824.

The spelling of 18216649 in words is "eighteen million, two hundred sixteen thousand, six hundred forty-nine".