21190177921 has 4 divisors (see below), whose sum is σ = 23116557744. Its totient is φ = 19263798100.

The previous prime is 21190177889. The next prime is 21190177927. The reversal of 21190177921 is 12977109112.

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.

It is a cyclic number.

It is not a de Polignac number, because 21190177921 - 2⁵ = 21190177889 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21190177927) 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, 963189895 + ... + 963189916.

It is an arithmetic number, because the mean of its divisors is an integer number (5779139436).

Almost surely, 2^21190177921 is an apocalyptic number.

It is an amenable number.

21190177921 is a deficient number, since it is larger than the sum of its proper divisors (1926379823).

21190177921 is a wasteful number, since it uses less digits than its factorization.

21190177921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1926379822.

The product of its (nonzero) digits is 15876, while the sum is 40.

The spelling of 21190177921 in words is "twenty-one billion, one hundred ninety million, one hundred seventy-seven thousand, nine hundred twenty-one".