999921951 has 12 divisors (see below), whose sum is σ = 1650664912. Its totient is φ = 571383936.

The previous prime is 999921947. The next prime is 999921977. The reversal of 999921951 is 159129999.

It is not a de Polignac number, because 999921951 - 2² = 999921947 is a prime.

It is a Duffinian number.

999921951 is a modest number, since divided by 21951 gives 9999 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999921931) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7935826 + ... + 7935951.

Almost surely, 2^999921951 is an apocalyptic number.

999921951 is a deficient number, since it is larger than the sum of its proper divisors (650742961).

999921951 is a wasteful number, since it uses less digits than its factorization.

999921951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15871790 (or 15871787 counting only the distinct ones).

The product of its digits is 590490, while the sum is 54.

The square root of 999921951 is about 31621.5425145580. The cubic root of 999921951 is about 999.9739829898.

The spelling of 999921951 in words is "nine hundred ninety-nine million, nine hundred twenty-one thousand, nine hundred fifty-one".