21820406 has 8 divisors (see below), whose sum is σ = 32947824. Its totient is φ = 10837800.

The previous prime is 21820391. The next prime is 21820411. The reversal of 21820406 is 60402812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21820406² = 952260236009672, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35825 + ... + 36428.

It is an arithmetic number, because the mean of its divisors is an integer number (4118478).

Almost surely, 2^21820406 is an apocalyptic number.

21820406 is a deficient number, since it is larger than the sum of its proper divisors (11127418).

21820406 is a wasteful number, since it uses less digits than its factorization.

21820406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72406.

The product of its (nonzero) digits is 768, while the sum is 23.

The square root of 21820406 is about 4671.2317433414. The cubic root of 21820406 is about 279.4393799683.

The spelling of 21820406 in words is "twenty-one million, eight hundred twenty thousand, four hundred six".