21380840 has 32 divisors (see below), whose sum is σ = 51808680. Its totient is φ = 7894272.

The previous prime is 21380813. The next prime is 21380851. The reversal of 21380840 is 4808312.

It can be written as a sum of positive squares in 4 ways, for example, as 15319396 + 6061444 = 3914^2 + 2462^2 .

It is a Harshad number since it is a multiple of its sum of digits (26).

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 20039 + ... + 21078.

Almost surely, 2^21380840 is an apocalyptic number.

21380840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21380840 is an abundant number, since it is smaller than the sum of its proper divisors (30427840).

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

21380840 is a wasteful number, since it uses less digits than its factorization.

21380840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41141 (or 41137 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 26.

The square root of 21380840 is about 4623.9420411593. The cubic root of 21380840 is about 277.5502276314.

The spelling of 21380840 in words is "twenty-one million, three hundred eighty thousand, eight hundred forty".