21691023 has 8 divisors (see below), whose sum is σ = 28951728. Its totient is φ = 14445504.

The previous prime is 21691013. The next prime is 21691037. The reversal of 21691023 is 32019612.

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

It is not a de Polignac number, because 21691023 - 2⁶ = 21690959 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21690984 and 21691002.

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 7 ways as a sum of consecutive naturals, for example, 115 + ... + 6587.

It is an arithmetic number, because the mean of its divisors is an integer number (3618966).

Almost surely, 2^21691023 is an apocalyptic number.

21691023 is a deficient number, since it is larger than the sum of its proper divisors (7260705).

21691023 is a wasteful number, since it uses less digits than its factorization.

21691023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7593.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21691023 is about 4657.3622362878. The cubic root of 21691023 is about 278.8859774820.

The spelling of 21691023 in words is "twenty-one million, six hundred ninety-one thousand, twenty-three".