21691004 has 12 divisors (see below), whose sum is σ = 37993704. Its totient is φ = 10835664.

The previous prime is 21691003. The next prime is 21691013. The reversal of 21691004 is 40019612.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21691003) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5042 + ... + 8294.

It is an arithmetic number, because the mean of its divisors is an integer number (3166142).

Almost surely, 2^21691004 is an apocalyptic number.

It is an amenable number.

21691004 is a deficient number, since it is larger than the sum of its proper divisors (16302700).

21691004 is a wasteful number, since it uses less digits than its factorization.

21691004 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4924 (or 4922 counting only the distinct ones).

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

The square root of 21691004 is about 4657.3601965062. The cubic root of 21691004 is about 278.8858960530.

The spelling of 21691004 in words is "twenty-one million, six hundred ninety-one thousand, four".