21506606 has 16 divisors (see below), whose sum is σ = 35538048. Its totient is φ = 9679800.

The previous prime is 21506593. The next prime is 21506609. The reversal of 21506606 is 60660512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506609) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2480 + ... + 7011.

It is an arithmetic number, because the mean of its divisors is an integer number (2221128).

Almost surely, 2^21506606 is an apocalyptic number.

21506606 is a deficient number, since it is larger than the sum of its proper divisors (14031442).

21506606 is a wasteful number, since it uses less digits than its factorization.

21506606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9607.

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 21506606 is about 4637.5215363381. The cubic root of 21506606 is about 278.0933644276.

The spelling of 21506606 in words is "twenty-one million, five hundred six thousand, six hundred six".