21690406 has 16 divisors (see below), whose sum is σ = 33799680. Its totient is φ = 10431880.

The previous prime is 21690397. The next prime is 21690407. The reversal of 21690406 is 60409612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690407) 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, 3591 + ... + 7501.

It is an arithmetic number, because the mean of its divisors is an integer number (2112480).

Almost surely, 2^21690406 is an apocalyptic number.

21690406 is a deficient number, since it is larger than the sum of its proper divisors (12109274).

21690406 is a wasteful number, since it uses less digits than its factorization.

21690406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4019.

The product of its (nonzero) digits is 2592, while the sum is 28.

The square root of 21690406 is about 4657.2959966058. The cubic root of 21690406 is about 278.8833331580.

The spelling of 21690406 in words is "twenty-one million, six hundred ninety thousand, four hundred six".