21949000921 has 4 divisors (see below), whose sum is σ = 21949315200. Its totient is φ = 21948686644.

The previous prime is 21949000903. The next prime is 21949000939. The reversal of 21949000921 is 12900094912.

21949000921 is a nontrivial binomial coefficient, being equal to C(209519, 2).

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21949000903) and next prime (21949000939).

It is not a de Polignac number, because 21949000921 - 2⁵ = 21949000889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21949010921) 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, 1 + ... + 209518.

It is an arithmetic number, because the mean of its divisors is an integer number (5487328800).

Almost surely, 2^21949000921 is an apocalyptic number.

21949000921 is the 209518-th triangular number.

21949000921 is the 69840-th centered nonagonal number.

It is an amenable number.

21949000921 is a deficient number, since it is larger than the sum of its proper divisors (314279).

21949000921 is a wasteful number, since it uses less digits than its factorization.

21949000921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 314278.

The product of its (nonzero) digits is 11664, while the sum is 37.

The spelling of 21949000921 in words is "twenty-one billion, nine hundred forty-nine million, nine hundred twenty-one", and thus it is an aban number.