21506272 has 24 divisors (see below), whose sum is σ = 42496272. Its totient is φ = 10713600.

The previous prime is 21506269. The next prime is 21506279. The reversal of 21506272 is 27260512.

It is a Smith number, since the sum of its digits (25) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506279) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8872 + ... + 11032.

It is an arithmetic number, because the mean of its divisors is an integer number (1770678).

Almost surely, 2^21506272 is an apocalyptic number.

It is an amenable number.

21506272 is a deficient number, since it is larger than the sum of its proper divisors (20990000).

21506272 is a wasteful number, since it uses less digits than its factorization.

21506272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2482 (or 2474 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21506272 is about 4637.4855255839. The cubic root of 21506272 is about 278.0919248132.

Adding to 21506272 its reverse (27260512), we get a palindrome (48766784).

The spelling of 21506272 in words is "twenty-one million, five hundred six thousand, two hundred seventy-two".