21897512087 has 16 divisors (see below), whose sum is σ = 24869935392. Its totient is φ = 19103454720.

The previous prime is 21897512071. The next prime is 21897512137. The reversal of 21897512087 is 78021579812.

It is a cyclic number.

It is not a de Polignac number, because 21897512087 - 2⁴ = 21897512071 is a prime.

It is a super-2 number, since 2×21897512087² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21897512047) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 338798 + ... + 398219.

It is an arithmetic number, because the mean of its divisors is an integer number (1554370962).

Almost surely, 2^21897512087 is an apocalyptic number.

21897512087 is a deficient number, since it is larger than the sum of its proper divisors (2972423305).

21897512087 is a wasteful number, since it uses less digits than its factorization.

21897512087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 737138.

The product of its (nonzero) digits is 564480, while the sum is 50.

The spelling of 21897512087 in words is "twenty-one billion, eight hundred ninety-seven million, five hundred twelve thousand, eighty-seven".