21671520 has 192 divisors, whose sum is σ = 77220864. Its totient is φ = 5068800.

The previous prime is 21671513. The next prime is 21671521. The reversal of 21671520 is 2517612.

It is a super-2 number, since 2×21671520² = 939309558220800, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21671521) 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 31 ways as a sum of consecutive naturals, for example, 143445 + ... + 143595.

It is an arithmetic number, because the mean of its divisors is an integer number (402192).

Almost surely, 2^21671520 is an apocalyptic number.

21671520 is a gapful number since it is divisible by the number (20) 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 21671520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38610432).

21671520 is an abundant number, since it is smaller than the sum of its proper divisors (55549344).

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

21671520 is a wasteful number, since it uses less digits than its factorization.

21671520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 205 (or 197 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21671520 is about 4655.2679836933. The cubic root of 21671520 is about 278.8023677143.

The spelling of 21671520 in words is "twenty-one million, six hundred seventy-one thousand, five hundred twenty".