21019406 has 4 divisors (see below), whose sum is σ = 31529112. Its totient is φ = 10509702.

The previous prime is 21019393. The next prime is 21019409. The reversal of 21019406 is 60491012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5254850 + ... + 5254853.

It is an arithmetic number, because the mean of its divisors is an integer number (7882278).

Almost surely, 2^21019406 is an apocalyptic number.

21019406 is a deficient number, since it is larger than the sum of its proper divisors (10509706).

21019406 is a wasteful number, since it uses less digits than its factorization.

21019406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10509705.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21019406 is about 4584.6925742082. The cubic root of 21019406 is about 275.9773750970.

The spelling of 21019406 in words is "twenty-one million, nineteen thousand, four hundred six".