21396906 has 16 divisors (see below), whose sum is σ = 47548800. Its totient is φ = 7132284.

The previous prime is 21396901. The next prime is 21396917. The reversal of 21396906 is 60969312.

It is not an unprimeable number, because it can be changed into a prime (21396901) 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, 198066 + ... + 198173.

It is an arithmetic number, because the mean of its divisors is an integer number (2971800).

Almost surely, 2^21396906 is an apocalyptic number.

21396906 is an abundant number, since it is smaller than the sum of its proper divisors (26151894).

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

21396906 is a wasteful number, since it uses less digits than its factorization.

21396906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396250 (or 396244 counting only the distinct ones).

The product of its (nonzero) digits is 17496, while the sum is 36.

The square root of 21396906 is about 4625.6789771881. The cubic root of 21396906 is about 277.6197291966.

It can be divided in two parts, 2139 and 6906, that added together give a triangular number (9045 = T₁₃₄).

The spelling of 21396906 in words is "twenty-one million, three hundred ninety-six thousand, nine hundred six".