21580739 has 4 divisors (see below), whose sum is σ = 22519056. Its totient is φ = 20642424.

The previous prime is 21580721. The next prime is 21580781. The reversal of 21580739 is 93708512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21580739 - 2¹⁶ = 21515203 is a prime.

It is a super-2 number, since 2×21580739² = 931456591572242, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21580699 and 21580708.

It is not an unprimeable number, because it can be changed into a prime (21580709) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 469124 + ... + 469169.

It is an arithmetic number, because the mean of its divisors is an integer number (5629764).

Almost surely, 2^21580739 is an apocalyptic number.

21580739 is a deficient number, since it is larger than the sum of its proper divisors (938317).

21580739 is an equidigital number, since it uses as much as digits as its factorization.

21580739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 938316.

The product of its (nonzero) digits is 15120, while the sum is 35.

The square root of 21580739 is about 4645.5073996282. The cubic root of 21580739 is about 278.4125261008.

The spelling of 21580739 in words is "twenty-one million, five hundred eighty thousand, seven hundred thirty-nine".