16215661 has 16 divisors (see below), whose sum is σ = 20338560. Its totient is φ = 12559680.

The previous prime is 16215659. The next prime is 16215677. The reversal of 16215661 is 16651261.

It is not a de Polignac number, because 16215661 - 2¹ = 16215659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16215631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14635 + ... + 15703.

It is an arithmetic number, because the mean of its divisors is an integer number (1271160).

Almost surely, 2^16215661 is an apocalyptic number.

16215661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16215661 is a deficient number, since it is larger than the sum of its proper divisors (4122899).

16215661 is a wasteful number, since it uses less digits than its factorization.

16215661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1284.

The product of its digits is 2160, while the sum is 28.

The square root of 16215661 is about 4026.8673928998. The cubic root of 16215661 is about 253.1113103606. Note that the first 3 decimals are identical.

Subtracting 16215661 from its reverse (16651261), we obtain a square (435600 = 660²).

The spelling of 16215661 in words is "sixteen million, two hundred fifteen thousand, six hundred sixty-one".