21031951 has 8 divisors (see below), whose sum is σ = 21450240. Its totient is φ = 20617752.

The previous prime is 21031909. The next prime is 21031973. The reversal of 21031951 is 15913012.

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

It is a cyclic number.

It is not a de Polignac number, because 21031951 - 2¹³ = 21023759 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031151) 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, 10626 + ... + 12448.

It is an arithmetic number, because the mean of its divisors is an integer number (2681280).

Almost surely, 2^21031951 is an apocalyptic number.

21031951 is a deficient number, since it is larger than the sum of its proper divisors (418289).

21031951 is a wasteful number, since it uses less digits than its factorization.

21031951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2045.

The product of its (nonzero) digits is 270, while the sum is 22.

The square root of 21031951 is about 4586.0605098494. The cubic root of 21031951 is about 276.0322679839.

Adding to 21031951 its reverse (15913012), we get a palindrome (36944963).

The spelling of 21031951 in words is "twenty-one million, thirty-one thousand, nine hundred fifty-one".