21661814 has 16 divisors (see below), whose sum is σ = 34013952. Its totient is φ = 10326888.

The previous prime is 21661813. The next prime is 21661831. The reversal of 21661814 is 41816612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19847 + ... + 20909.

It is an arithmetic number, because the mean of its divisors is an integer number (2125872).

Almost surely, 2^21661814 is an apocalyptic number.

21661814 is a deficient number, since it is larger than the sum of its proper divisors (12352138).

21661814 is a wasteful number, since it uses less digits than its factorization.

21661814 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1531.

The product of its digits is 2304, while the sum is 29.

The square root of 21661814 is about 4654.2253920497. The cubic root of 21661814 is about 278.7607391949.

The spelling of 21661814 in words is "twenty-one million, six hundred sixty-one thousand, eight hundred fourteen".