21400520 has 16 divisors (see below), whose sum is σ = 48151260. Its totient is φ = 8560192.

The previous prime is 21400507. The next prime is 21400523. The reversal of 21400520 is 2500412.

It can be written as a sum of positive squares in 2 ways, for example, as 21362884 + 37636 = 4622^2 + 194^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21400495 and 21400504.

It is not an unprimeable number, because it can be changed into a prime (21400523) 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 3 ways as a sum of consecutive naturals, for example, 267467 + ... + 267546.

Almost surely, 2^21400520 is an apocalyptic number.

21400520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21400520 is an abundant number, since it is smaller than the sum of its proper divisors (26750740).

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

21400520 is a wasteful number, since it uses less digits than its factorization.

21400520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 535024 (or 535020 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 14.

The square root of 21400520 is about 4626.0696060479. The cubic root of 21400520 is about 277.6353585780.

Adding to 21400520 its reverse (2500412), we get a palindrome (23900932).

The spelling of 21400520 in words is "twenty-one million, four hundred thousand, five hundred twenty".