21671580 has 48 divisors (see below), whose sum is σ = 69350400. Its totient is φ = 4953408.

The previous prime is 21671567. The next prime is 21671581. The reversal of 21671580 is 8517612.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21671581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25380 + ... + 26219.

It is an arithmetic number, because the mean of its divisors is an integer number (1444800).

Almost surely, 2^21671580 is an apocalyptic number.

21671580 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21671580 is an abundant number, since it is smaller than the sum of its proper divisors (47678820).

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

21671580 is a wasteful number, since it uses less digits than its factorization.

21671580 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51618 (or 51616 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 21671580 is about 4655.2744280010. The cubic root of 21671580 is about 278.8026250124.

The spelling of 21671580 in words is "twenty-one million, six hundred seventy-one thousand, five hundred eighty".