21250440 has 48 divisors (see below), whose sum is σ = 69065100. Its totient is φ = 5666688.

The previous prime is 21250429. The next prime is 21250451. The reversal of 21250440 is 4405212.

It is an interprime number because it is at equal distance from previous prime (21250429) and next prime (21250451).

It can be written as a sum of positive squares in 2 ways, for example, as 19766916 + 1483524 = 4446^2 + 1218^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29155 + ... + 29874.

Almost surely, 2^21250440 is an apocalyptic number.

21250440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21250440 is an abundant number, since it is smaller than the sum of its proper divisors (47814660).

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

21250440 is a wasteful number, since it uses less digits than its factorization.

21250440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59046 (or 59039 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21250440 is about 4609.8199531001. The cubic root of 21250440 is about 276.9848245497.

Adding to 21250440 its reverse (4405212), we get a palindrome (25655652).

The spelling of 21250440 in words is "twenty-one million, two hundred fifty thousand, four hundred forty".