21691642 has 8 divisors (see below), whose sum is σ = 37185696. Its totient is φ = 9296412.

The previous prime is 21691633. The next prime is 21691693. The reversal of 21691642 is 24619612.

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 774688 + ... + 774715.

It is an arithmetic number, because the mean of its divisors is an integer number (4648212).

Almost surely, 2^21691642 is an apocalyptic number.

21691642 is a deficient number, since it is larger than the sum of its proper divisors (15494054).

21691642 is a wasteful number, since it uses less digits than its factorization.

21691642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1549412.

The product of its digits is 5184, while the sum is 31.

The square root of 21691642 is about 4657.4286897386. The cubic root of 21691642 is about 278.8886303272. Note that the first 3 decimals are identical.

The spelling of 21691642 in words is "twenty-one million, six hundred ninety-one thousand, six hundred forty-two".