21211219978 has 16 divisors (see below), whose sum is σ = 34267224096. Its totient is φ = 9788952240.

The previous prime is 21211219973. The next prime is 21211220021. The reversal of 21211219978 is 87991211212.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21211219973) 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, 355093 + ... + 410503.

It is an arithmetic number, because the mean of its divisors is an integer number (2141701506).

Almost surely, 2^21211219978 is an apocalyptic number.

21211219978 is a deficient number, since it is larger than the sum of its proper divisors (13056004118).

21211219978 is a wasteful number, since it uses less digits than its factorization.

21211219978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70149.

The product of its digits is 36288, while the sum is 43.

The spelling of 21211219978 in words is "twenty-one billion, two hundred eleven million, two hundred nineteen thousand, nine hundred seventy-eight".