21660144 has 40 divisors (see below), whose sum is σ = 61043712. Its totient is φ = 6563520.

The previous prime is 21660137. The next prime is 21660151. The reversal of 21660144 is 44106612.

It is an interprime number because it is at equal distance from previous prime (21660137) and next prime (21660151).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19984 + ... + 21039.

Almost surely, 2^21660144 is an apocalyptic number.

21660144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21660144 is an abundant number, since it is smaller than the sum of its proper divisors (39383568).

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

21660144 is a wasteful number, since it uses less digits than its factorization.

21660144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41045 (or 41039 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21660144 is about 4654.0459817239. The cubic root of 21660144 is about 278.7535753997.

Adding to 21660144 its reverse (44106612), we get a palindrome (65766756).

The spelling of 21660144 in words is "twenty-one million, six hundred sixty thousand, one hundred forty-four".