21507404 has 12 divisors (see below), whose sum is σ = 37677864. Its totient is φ = 10742304.

The previous prime is 21507389. The next prime is 21507413. The reversal of 21507404 is 40470512.

It is a self number, because there is not a number n which added to its sum of digits gives 21507404.

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, 2519 + ... + 7025.

It is an arithmetic number, because the mean of its divisors is an integer number (3139822).

Almost surely, 2^21507404 is an apocalyptic number.

It is an amenable number.

21507404 is a deficient number, since it is larger than the sum of its proper divisors (16170460).

21507404 is a wasteful number, since it uses less digits than its factorization.

21507404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5704 (or 5702 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21507404 is about 4637.6075728763. The cubic root of 21507404 is about 278.0968039253.

Adding to 21507404 its reverse (40470512), we get a palindrome (61977916).

The spelling of 21507404 in words is "twenty-one million, five hundred seven thousand, four hundred four".