21691386 has 24 divisors (see below), whose sum is σ = 47567520. Its totient is φ = 7142856.

The previous prime is 21691381. The next prime is 21691403. The reversal of 21691386 is 68319612.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21691386.

It is not an unprimeable number, because it can be changed into a prime (21691381) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5766 + ... + 8753.

It is an arithmetic number, because the mean of its divisors is an integer number (1981980).

Almost surely, 2^21691386 is an apocalyptic number.

21691386 is an abundant number, since it is smaller than the sum of its proper divisors (25876134).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21691386 is a wasteful number, since it uses less digits than its factorization.

21691386 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14610 (or 14607 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 21691386 is about 4657.4012066817. The cubic root of 21691386 is about 278.8875331954.

The spelling of 21691386 in words is "twenty-one million, six hundred ninety-one thousand, three hundred eighty-six".