1972721521 has 8 divisors (see below), whose sum is σ = 1984653440. Its totient is φ = 1960825968.

The previous prime is 1972721473. The next prime is 1972721551. The reversal of 1972721521 is 1251272791.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 1972721521 - 2⁷ = 1972721393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1972721551) 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, 103915 + ... + 121423.

It is an arithmetic number, because the mean of its divisors is an integer number (248081680).

Almost surely, 2^1972721521 is an apocalyptic number.

It is an amenable number.

1972721521 is a deficient number, since it is larger than the sum of its proper divisors (11931919).

1972721521 is a wasteful number, since it uses less digits than its factorization.

1972721521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18183.

The product of its digits is 17640, while the sum is 37.

The square root of 1972721521 is about 44415.3297972671. The cubic root of 1972721521 is about 1254.1666866920.

The spelling of 1972721521 in words is "one billion, nine hundred seventy-two million, seven hundred twenty-one thousand, five hundred twenty-one".