21391907954 has 4 divisors (see below), whose sum is σ = 32087861934. Its totient is φ = 10695953976.

The previous prime is 21391907951. The next prime is 21391907963. The reversal of 21391907954 is 45970919312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20441850625 + 950057329 = 142975^2 + 30823^2 .

It is a super-2 number, since 2×21391907954² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21391907951) 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 as a sum of consecutive naturals, namely, 5347976987 + ... + 5347976990.

Almost surely, 2^21391907954 is an apocalyptic number.

21391907954 is a deficient number, since it is larger than the sum of its proper divisors (10695953980).

21391907954 is a wasteful number, since it uses less digits than its factorization.

21391907954 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10695953979.

The product of its (nonzero) digits is 612360, while the sum is 50.

The spelling of 21391907954 in words is "twenty-one billion, three hundred ninety-one million, nine hundred seven thousand, nine hundred fifty-four".