51721989 has 8 divisors (see below), whose sum is σ = 75232032. Its totient is φ = 31346640.

The previous prime is 51721927. The next prime is 51721997. The reversal of 51721989 is 98912715.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 51721989 - 2⁷ = 51721861 is a prime.

It is a super-2 number, since 2×51721989² = 5350328292232242, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 51721989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51721909) 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, 783634 + ... + 783699.

It is an arithmetic number, because the mean of its divisors is an integer number (9404004).

Almost surely, 2^51721989 is an apocalyptic number.

It is an amenable number.

51721989 is a deficient number, since it is larger than the sum of its proper divisors (23510043).

51721989 is a wasteful number, since it uses less digits than its factorization.

51721989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1567347.

The product of its digits is 45360, while the sum is 42.

The square root of 51721989 is about 7191.8001223616. The cubic root of 51721989 is about 372.5847477700.

The spelling of 51721989 in words is "fifty-one million, seven hundred twenty-one thousand, nine hundred eighty-nine".