21165456 has 80 divisors (see below), whose sum is σ = 59621184. Its totient is φ = 6431232.

The previous prime is 21165427. The next prime is 21165457. The reversal of 21165456 is 65456112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21165457) 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 15 ways as a sum of consecutive naturals, for example, 66610 + ... + 66926.

Almost surely, 2^21165456 is an apocalyptic number.

21165456 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21165456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29810592).

21165456 is an abundant number, since it is smaller than the sum of its proper divisors (38455728).

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

21165456 is a wasteful number, since it uses less digits than its factorization.

21165456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 448 (or 442 counting only the distinct ones).

The product of its digits is 7200, while the sum is 30.

The square root of 21165456 is about 4600.5930052549. The cubic root of 21165456 is about 276.6150953052.

The spelling of 21165456 in words is "twenty-one million, one hundred sixty-five thousand, four hundred fifty-six".