21987951351 has 32 divisors (see below), whose sum is σ = 32133024000. Its totient is φ = 13311997440.

The previous prime is 21987951331. The next prime is 21987951353. The reversal of 21987951351 is 15315978912.

It is not a de Polignac number, because 21987951351 - 2⁶ = 21987951287 is a prime.

It is a super-2 number, since 2×21987951351² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a junction number, because it is equal to n+sod(n) for n = 21987951294 and 21987951303.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987951353) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2852100 + ... + 2859798.

It is an arithmetic number, because the mean of its divisors is an integer number (1004157000).

Almost surely, 2^21987951351 is an apocalyptic number.

21987951351 is a deficient number, since it is larger than the sum of its proper divisors (10145072649).

21987951351 is a wasteful number, since it uses less digits than its factorization.

21987951351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9679.

The product of its digits is 680400, while the sum is 51.

The spelling of 21987951351 in words is "twenty-one billion, nine hundred eighty-seven million, nine hundred fifty-one thousand, three hundred fifty-one".