21471240 has 64 divisors (see below), whose sum is σ = 73618560. Its totient is φ = 4907520.

The previous prime is 21471239. The next prime is 21471257. The reversal of 21471240 is 4217412.

It is a happy number.

It is a super-2 number, since 2×21471240² = 922028294275200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11941 + ... + 13620.

It is an arithmetic number, because the mean of its divisors is an integer number (1150290).

Almost surely, 2^21471240 is an apocalyptic number.

21471240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21471240 is an abundant number, since it is smaller than the sum of its proper divisors (52147320).

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

21471240 is a wasteful number, since it uses less digits than its factorization.

21471240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25582 (or 25578 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 21471240 is about 4633.7069393737. The cubic root of 21471240 is about 277.9408462377.

Adding to 21471240 its reverse (4217412), we get a palindrome (25688652).

The spelling of 21471240 in words is "twenty-one million, four hundred seventy-one thousand, two hundred forty".