21475840 has 40 divisors (see below), whose sum is σ = 51497820. Its totient is φ = 8589312.

The previous prime is 21475837. The next prime is 21475889. The reversal of 21475840 is 4857412.

It can be written as a sum of positive squares in 2 ways, for example, as 21086464 + 389376 = 4592^2 + 624^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a super-2 number, since 2×21475840² = 922423407411200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1635 + ... + 6754.

Almost surely, 2^21475840 is an apocalyptic number.

21475840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21475840 is an abundant number, since it is smaller than the sum of its proper divisors (30021980).

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

21475840 is an frugal number, since it uses more digits than its factorization.

21475840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8412 (or 8396 counting only the distinct ones).

The product of its (nonzero) digits is 8960, while the sum is 31.

The square root of 21475840 is about 4634.2032756451. The cubic root of 21475840 is about 277.9606935094.

The spelling of 21475840 in words is "twenty-one million, four hundred seventy-five thousand, eight hundred forty".