21247408 has 40 divisors (see below), whose sum is σ = 50670368. Its totient is φ = 8404992.

The previous prime is 21247393. The next prime is 21247411. The reversal of 21247408 is 80474212.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5841 + ... + 8752.

Almost surely, 2^21247408 is an apocalyptic number.

21247408 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21247408 is an abundant number, since it is smaller than the sum of its proper divisors (29422960).

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

21247408 is a wasteful number, since it uses less digits than its factorization.

21247408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14621 (or 14615 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 28.

The square root of 21247408 is about 4609.4910781994. The cubic root of 21247408 is about 276.9716505804.

It can be divided in two parts, 2 and 1247408, that added together give a triangular number (1247410 = T₁₅₇₉).

The spelling of 21247408 in words is "twenty-one million, two hundred forty-seven thousand, four hundred eight".