21490506 has 24 divisors (see below), whose sum is σ = 46716384. Its totient is φ = 7139880.

The previous prime is 21490459. The next prime is 21490517. The reversal of 21490506 is 60509412.

It is a self number, because there is not a number n which added to its sum of digits gives 21490506.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4155 + ... + 7761.

It is an arithmetic number, because the mean of its divisors is an integer number (1946516).

Almost surely, 2^21490506 is an apocalyptic number.

21490506 is an abundant number, since it is smaller than the sum of its proper divisors (25225878).

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

21490506 is a wasteful number, since it uses less digits than its factorization.

21490506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3946 (or 3943 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21490506 is about 4635.7853703553. The cubic root of 21490506 is about 278.0239528729.

Adding to 21490506 its reverse (60509412), we get a palindrome (81999918).

The spelling of 21490506 in words is "twenty-one million, four hundred ninety thousand, five hundred six".