21329691 has 16 divisors (see below), whose sum is σ = 29189376. Its totient is φ = 13849056.

The previous prime is 21329683. The next prime is 21329699. The reversal of 21329691 is 19692312.

It is an interprime number because it is at equal distance from previous prime (21329683) and next prime (21329699).

It is not a de Polignac number, because 21329691 - 2³ = 21329683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21329699) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 25506 + ... + 26328.

It is an arithmetic number, because the mean of its divisors is an integer number (1824336).

Almost surely, 2^21329691 is an apocalyptic number.

21329691 is the 2469-th nonagonal number.

21329691 is a deficient number, since it is larger than the sum of its proper divisors (7859685).

21329691 is a wasteful number, since it uses less digits than its factorization.

21329691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1042.

The product of its digits is 5832, while the sum is 33.

The square root of 21329691 is about 4618.4078425362. The cubic root of 21329691 is about 277.3287247614.

The spelling of 21329691 in words is "twenty-one million, three hundred twenty-nine thousand, six hundred ninety-one".