21177540 has 72 divisors (see below), whose sum is σ = 66470040. Its totient is φ = 5451264.

The previous prime is 21177539. The next prime is 21177577. The reversal of 21177540 is 4577112.

21177540 is a `hidden beast` number, since 2 + 117 + 7 + 540 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 2359296 + 18818244 = 1536^2 + 4338^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3192 + ... + 7248.

It is an arithmetic number, because the mean of its divisors is an integer number (923195).

Almost surely, 2^21177540 is an apocalyptic number.

21177540 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 21177540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33235020).

21177540 is an abundant number, since it is smaller than the sum of its proper divisors (45292500).

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

21177540 is a wasteful number, since it uses less digits than its factorization.

21177540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4101 (or 4096 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21177540 is about 4601.9061268131. The cubic root of 21177540 is about 276.6677279358.

The spelling of 21177540 in words is "twenty-one million, one hundred seventy-seven thousand, five hundred forty".