21430506 has 32 divisors (see below), whose sum is σ = 45601920. Its totient is φ = 6714048.

The previous prime is 21430481. The next prime is 21430529. The reversal of 21430506 is 60503412.

It is a happy number.

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, 29115 + ... + 29841.

It is an arithmetic number, because the mean of its divisors is an integer number (1425060).

Almost surely, 2^21430506 is an apocalyptic number.

21430506 is an abundant number, since it is smaller than the sum of its proper divisors (24171414).

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

21430506 is an equidigital number, since it uses as much as digits as its factorization.

21430506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 783 (or 749 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21430506 is about 4629.3094517433. The cubic root of 21430506 is about 277.7649705147.

Adding to 21430506 its reverse (60503412), we get a palindrome (81933918).

The spelling of 21430506 in words is "twenty-one million, four hundred thirty thousand, five hundred six".