21305739 has 24 divisors (see below), whose sum is σ = 35590800. Its totient is φ = 11237184.

The previous prime is 21305737. The next prime is 21305741. The reversal of 21305739 is 93750312.

It is an interprime number because it is at equal distance from previous prime (21305737) and next prime (21305741).

It is not a de Polignac number, because 21305739 - 2¹ = 21305737 is a prime.

It is a super-2 number, since 2×21305739² = 907869028672242, which contains 22 as substring.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21305737) 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 23 ways as a sum of consecutive naturals, for example, 3664 + ... + 7485.

It is an arithmetic number, because the mean of its divisors is an integer number (1482950).

Almost surely, 2^21305739 is an apocalyptic number.

21305739 is a deficient number, since it is larger than the sum of its proper divisors (14285061).

21305739 is a wasteful number, since it uses less digits than its factorization.

21305739 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11179 (or 11172 counting only the distinct ones).

The product of its (nonzero) digits is 5670, while the sum is 30.

The square root of 21305739 is about 4615.8140127176. The cubic root of 21305739 is about 277.2248778815.

The spelling of 21305739 in words is "twenty-one million, three hundred five thousand, seven hundred thirty-nine".