21349681 has 8 divisors (see below), whose sum is σ = 22656960. Its totient is φ = 20074032.

The previous prime is 21349667. The next prime is 21349687. The reversal of 21349681 is 18694312.

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

It is not a de Polignac number, because 21349681 - 2¹¹ = 21347633 is a prime.

It is a super-2 number, since 2×21349681² = 911617757603522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21349687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6510 + ... + 9223.

It is an arithmetic number, because the mean of its divisors is an integer number (2832120).

Almost surely, 2^21349681 is an apocalyptic number.

It is an amenable number.

21349681 is a deficient number, since it is larger than the sum of its proper divisors (1307279).

21349681 is a wasteful number, since it uses less digits than its factorization.

21349681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15815.

The product of its digits is 10368, while the sum is 34.

The square root of 21349681 is about 4620.5715014487. The cubic root of 21349681 is about 277.4153343961.

It can be divided in two parts, 213 and 49681, that added together give a palindrome (49894).

The spelling of 21349681 in words is "twenty-one million, three hundred forty-nine thousand, six hundred eighty-one".