21210999957 has 20 divisors (see below), whose sum is σ = 36212078496. Its totient is φ = 12120571080.

The previous prime is 21210999917. The next prime is 21210999973. The reversal of 21210999957 is 75999901212.

It is not a de Polignac number, because 21210999957 - 2¹⁰ = 21210998933 is a prime.

It is a super-5 number, since 5×21210999957⁵ (a number of 53 digits) contains 55555 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210999917) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 18704019 + ... + 18705152.

Almost surely, 2^21210999957 is an apocalyptic number.

21210999957 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21210999957 is a deficient number, since it is larger than the sum of its proper divisors (15001078539).

21210999957 is an equidigital number, since it uses as much as digits as its factorization.

21210999957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37409190 (or 37409181 counting only the distinct ones).

The product of its (nonzero) digits is 918540, while the sum is 54.

The spelling of 21210999957 in words is "twenty-one billion, two hundred ten million, nine hundred ninety-nine thousand, nine hundred fifty-seven".