2151985621 has 4 divisors (see below), whose sum is σ = 2221404544. Its totient is φ = 2082566700.

The previous prime is 2151985597. The next prime is 2151985631. The reversal of 2151985621 is 1265891512.

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 2151985621 - 2⁹ = 2151985109 is a prime.

It is a super-2 number, since 2×2151985621² = 9262084225981511282, 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 (2151985631) 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, 34709415 + ... + 34709476.

It is an arithmetic number, because the mean of its divisors is an integer number (555351136).

Almost surely, 2^2151985621 is an apocalyptic number.

It is an amenable number.

2151985621 is a deficient number, since it is larger than the sum of its proper divisors (69418923).

2151985621 is an equidigital number, since it uses as much as digits as its factorization.

2151985621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69418922.

The product of its digits is 43200, while the sum is 40.

The square root of 2151985621 is about 46389.4990380366. The cubic root of 2151985621 is about 1291.0600866866.

The spelling of 2151985621 in words is "two billion, one hundred fifty-one million, nine hundred eighty-five thousand, six hundred twenty-one".