21180691 has 24 divisors (see below), whose sum is σ = 26692416. Its totient is φ = 16692480.

The previous prime is 21180683. The next prime is 21180697. The reversal of 21180691 is 19608112.

It is a happy number.

It is not a de Polignac number, because 21180691 - 2³ = 21180683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21180697) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 38881 + ... + 39421.

It is an arithmetic number, because the mean of its divisors is an integer number (1112184).

Almost surely, 2^21180691 is an apocalyptic number.

21180691 is a deficient number, since it is larger than the sum of its proper divisors (5511725).

21180691 is a wasteful number, since it uses less digits than its factorization.

21180691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 619 (or 612 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 21180691 is about 4602.2484722144. The cubic root of 21180691 is about 276.6814490255.

The spelling of 21180691 in words is "twenty-one million, one hundred eighty thousand, six hundred ninety-one".