21579540 has 48 divisors (see below), whose sum is σ = 60631872. Its totient is φ = 5734656.

The previous prime is 21579517. The next prime is 21579557. The reversal of 21579540 is 4597512.

It is a super-2 number, since 2×21579540² = 931353093223200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27027 + ... + 27813.

It is an arithmetic number, because the mean of its divisors is an integer number (1263164).

Almost surely, 2^21579540 is an apocalyptic number.

21579540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21579540 is an abundant number, since it is smaller than the sum of its proper divisors (39052332).

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

21579540 is a wasteful number, since it uses less digits than its factorization.

21579540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1256 (or 1254 counting only the distinct ones).

The product of its (nonzero) digits is 12600, while the sum is 33.

The square root of 21579540 is about 4645.3783484233. The cubic root of 21579540 is about 278.4073699165.

The spelling of 21579540 in words is "twenty-one million, five hundred seventy-nine thousand, five hundred forty".