21051031 has 8 divisors (see below), whose sum is σ = 22303280. Its totient is φ = 19813248.

The previous prime is 21051029. The next prime is 21051047. The reversal of 21051031 is 13015012.

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

It is a 7-Lehmer number, since φ(21051031) divides (21051031-1)⁷.

It is a cyclic number.

It is not a de Polignac number, because 21051031 - 2¹ = 21051029 is a prime.

It is a super-2 number, since 2×21051031² = 886291812325922, 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 (21051011) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 546 + ... + 6511.

It is an arithmetic number, because the mean of its divisors is an integer number (2787910).

Almost surely, 2^21051031 is an apocalyptic number.

21051031 is a deficient number, since it is larger than the sum of its proper divisors (1252249).

21051031 is a wasteful number, since it uses less digits than its factorization.

21051031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7233.

The product of its (nonzero) digits is 30, while the sum is 13.

The square root of 21051031 is about 4588.1402550489. The cubic root of 21051031 is about 276.1157140995.

Adding to 21051031 its reverse (13015012), we get a palindrome (34066043).

It can be divided in two parts, 2105 and 1031, that added together give a square (3136 = 56²).

The spelling of 21051031 in words is "twenty-one million, fifty-one thousand, thirty-one".