21397806 has 24 divisors (see below), whose sum is σ = 46476144. Its totient is φ = 7115040.

The previous prime is 21397787. The next prime is 21397807. The reversal of 21397806 is 60879312.

It is a super-2 number, since 2×21397806² = 915732203227272, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21397807) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7546 + ... + 9986.

It is an arithmetic number, because the mean of its divisors is an integer number (1936506).

Almost surely, 2^21397806 is an apocalyptic number.

21397806 is an abundant number, since it is smaller than the sum of its proper divisors (25078338).

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

21397806 is a wasteful number, since it uses less digits than its factorization.

21397806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2936 (or 2933 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21397806 is about 4625.7762591807. The cubic root of 21397806 is about 277.6236215701.

The spelling of 21397806 in words is "twenty-one million, three hundred ninety-seven thousand, eight hundred six".