21021214957 has 4 divisors (see below), whose sum is σ = 21075254460. Its totient is φ = 20967175456.

The previous prime is 21021214939. The next prime is 21021214993. The reversal of 21021214957 is 75941212012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1474099236 + 19547115721 = 38394^2 + 139811^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021214957 - 2¹¹ = 21021212909 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 (21021214937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27019168 + ... + 27019945.

It is an arithmetic number, because the mean of its divisors is an integer number (5268813615).

Almost surely, 2^21021214957 is an apocalyptic number.

It is an amenable number.

21021214957 is a deficient number, since it is larger than the sum of its proper divisors (54039503).

21021214957 is an equidigital number, since it uses as much as digits as its factorization.

21021214957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54039502.

The product of its (nonzero) digits is 10080, while the sum is 34.

Adding to 21021214957 its reverse (75941212012), we get a palindrome (96962426969).

The spelling of 21021214957 in words is "twenty-one billion, twenty-one million, two hundred fourteen thousand, nine hundred fifty-seven".