21399955390 has 16 divisors (see below), whose sum is σ = 42021730800. Its totient is φ = 7781801920.

The previous prime is 21399955387. The next prime is 21399955391. The reversal of 21399955390 is 9355999312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (55).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21399955391) 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, 97272415 + ... + 97272634.

It is an arithmetic number, because the mean of its divisors is an integer number (2626358175).

Almost surely, 2^21399955390 is an apocalyptic number.

21399955390 is a deficient number, since it is larger than the sum of its proper divisors (20621775410).

21399955390 is a wasteful number, since it uses less digits than its factorization.

21399955390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 194545067.

The product of its (nonzero) digits is 2952450, while the sum is 55.

The spelling of 21399955390 in words is "twenty-one billion, three hundred ninety-nine million, nine hundred fifty-five thousand, three hundred ninety".