21987958394 has 16 divisors (see below), whose sum is σ = 33854692608. Its totient is φ = 10705436112.

The previous prime is 21987958387. The next prime is 21987958397. The reversal of 21987958394 is 49385978912.

It is a self number, because there is not a number n which added to its sum of digits gives 21987958394.

It is not an unprimeable number, because it can be changed into a prime (21987958397) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 575174 + ... + 612209.

It is an arithmetic number, because the mean of its divisors is an integer number (2115918288).

Almost surely, 2^21987958394 is an apocalyptic number.

21987958394 is a deficient number, since it is larger than the sum of its proper divisors (11866734214).

21987958394 is a wasteful number, since it uses less digits than its factorization.

21987958394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1187629.

The product of its digits is 39191040, while the sum is 65.

The spelling of 21987958394 in words is "twenty-one billion, nine hundred eighty-seven million, nine hundred fifty-eight thousand, three hundred ninety-four".