21070331 has 4 divisors (see below), whose sum is σ = 21139272. Its totient is φ = 21001392.

The previous prime is 21070321. The next prime is 21070337. The reversal of 21070331 is 13307012.

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 21070331 - 2⁶ = 21070267 is a prime.

It is a super-2 number, since 2×21070331² = 887917696899122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21070337) 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, 34010 + ... + 34623.

It is an arithmetic number, because the mean of its divisors is an integer number (5284818).

Almost surely, 2^21070331 is an apocalyptic number.

21070331 is a deficient number, since it is larger than the sum of its proper divisors (68941).

21070331 is an equidigital number, since it uses as much as digits as its factorization.

21070331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68940.

The product of its (nonzero) digits is 126, while the sum is 17.

The square root of 21070331 is about 4590.2430218889. The cubic root of 21070331 is about 276.2000711004.

Adding to 21070331 its reverse (13307012), we get a palindrome (34377343).

The spelling of 21070331 in words is "twenty-one million, seventy thousand, three hundred thirty-one".