21712031 has 4 divisors (see below), whose sum is σ = 23685864. Its totient is φ = 19738200.

The previous prime is 21711973. The next prime is 21712057. The reversal of 21712031 is 13021712.

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 21712031 - 2⁶ = 21711967 is a prime.

It is a super-2 number, since 2×21712031² = 942824580289922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21712331) 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, 986900 + ... + 986921.

It is an arithmetic number, because the mean of its divisors is an integer number (5921466).

Almost surely, 2^21712031 is an apocalyptic number.

21712031 is a deficient number, since it is larger than the sum of its proper divisors (1973833).

21712031 is a wasteful number, since it uses less digits than its factorization.

21712031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1973832.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21712031 is about 4659.6170443503. The cubic root of 21712031 is about 278.9759831675.

Adding to 21712031 its reverse (13021712), we get a palindrome (34733743).

The spelling of 21712031 in words is "twenty-one million, seven hundred twelve thousand, thirty-one".